- Main Antagonists are villains who pose a serious threat to the main characters, especially Dexter. There are always one or more main antagonists per season, and all but one visit Miami Metro at least once.
- Secondary Antagonists are villains that Dexter (or other characters) encounter at least two times per novel/season. They usually serve as a sub-plot, but may be connected to the main antagonists.
Also, while most are serial killers, there are examples of antagonists who are not serial killers and even a few who have no known murders.
- Brian Moser, under the alias Rudy Cooper, is the first season's Main antagonist. Dubbed The Ice Truck Killer, Brian is actually Dexter's older brother and uses his victims in an elaborate scheme to help Dexter remember his past and reunite them as a family. Dexter eventually uncovers his origins, but rejects Brian in favor of the life he has managed to live using The Code of Harry. Knowing Brian will never stop trying to "free" him from his normal life, Dexter kills him, making it look like a suicide. Brian (under the alias Rudy Cooper) visits Miami Metro a few times to meet with Debra Morgan.
- Carlos Guerrero - a powerful mobster who puts against himself a great deal of policemen and even Dexter himself because of brutal murder by proxy in which a cop and his wife died.
- Sergeant James Doakes, who only starts to really suspect Dexter near the end of the season, shifting to Main category effectively.
- Detective McNamara can also be considered an antagonist in Doakes' plot, though a temporary minor one. The reason behind Mac being an antagonist is strictly the bare basis of the term...he opposes Doakes, views him as his enemy and does what he can to get back at him.
- Paul Bennett is also an antagonist in Rita's sub-plot.
- Lila West, whom Dexter meets while attending a Narcotics Anonymous meeting (an act he is putting on as part of a lie to Rita) is a sociopath with a propensity to burn things. She and Dexter form a complicated relationship, as Dexter believes she can help him resist his Dark Passenger, while Lila believes Dexter is her soulmate and is willing to harm anyone whom she sees an obstacle to them being together. Dexter eventually realizes her dark obsession with him and breaks things off, which leads to Lila stalking him and the other people in his life. When Dexter rejects her again, Lila tries to kill him along with Astor and Cody before fleeing the country. Dexter eventually tracks her down in Paris where he quickly kills her, using drugs on her to keep her from feeling the pain. Lila visits Miami Metro to meet with Dexter a few times.
- Sgt. James Doakes, who always found Dexter strange, is now convinced that Dexter is up to no good and actively stalks him, which prevents Dexter from satisfying his homicidal urges. Dexter is able to shake him for a while, but Doakes eventually catches Dexter red-handed by placing a GPS tracker on his boat, the Slice of Life. Dexter manages to overpower Doakes and holds him captive for several days inside a remote cabin in the Everglades. Even though it would make life easier for him, Dexter refuses to kill Doakes because he does not fit the code. During his captivity, Doakes and Dexter have several conversations that show the two understand each other more than either was willing to admit before. Instead of killing Doakes, Dexter begins planting evidence to frame him for Dexter's own crimes. The last time Dexter and Doakes speak, Dexter tells him he really enjoyed being able to speak openly and honestly with him. Lila West and Doakes meet for the first and only time when a distraught Lila steals Dexter's GPS and uses it to find the cabin, where she finds Doakes still in captivity. Doakes reveals that Dexter is a serial killer, but rather than set him free, Lila decides to kill Doakes to remove another threat to her relationship with Dexter. She blows up the cabin, killing Doakes and inadvertently completing Dexter's frame job. Doakes works at Miami-Metro most of the time within two seasons, but after he attacks Dexter, he gets fired and later visits Metro as a witness, on Lundy's request.
- Santos Jimenez - one of the men who aided in the death of Laura Moser and attempted to kill Dexter after being confronted and brutally beaten by him. He is later killed by Dexter in the same way he himself killed Laura (karma).
- ADA Miguel Prado is the main antagonist and becomes part of Dexter's life as result of Dexter's victim Fred "Freebo" Bowman. When Dexter first attempts to kill Freebo, he is attacked by Miguel's brother Oscar, whom he kills in self-defense. Dexter is able to frame Freebo for the crime, but after hunting down and killing Freebo himself, he is caught by Miguel. Instead of turning Dexter in, Miguel thanks him.. An uneasy trust builds between the two men, and Dexter eventually opens up about his other vigilante murders after Miguel makes it clear he supports such a thing and shows an interest in participating himself. Though Dexter resists at first, he eventually teaches Miguel some of his methods and code. After Miguel commits his first murder with Dexter, though, he develops blood lust and murders a defense attorney he dislikes. When Dexter chastises Miguel for this, their friendship falls apart and they struggle to gain leverage over each other. Dexter ultimately stops Miguel by strangling him to death, and frames the murder on King; though Dexter is not heavily involved with the Skinner case, he knows enough to copy King's M.O. Miguel visits Miami Metro a few times to talk with LaGuerta about shared cases or to catch up with Dexter. George visits it as a witness.
- George King, whom the Miami Metro Police refer to as "The Skinner," a former Nicaraguan solider working as a tree-trimmer, begins searching for Freebo, who owes him a large sum of money. Unable to find Freebo, he begins torturing and killing those with ties to him. He is dubbed "The Skinner" due to his chosen method of torture. King is eventually arrested for the abduction and torture of Anton Briggs, but Miguel, in an effort to have Dexter taken out, uses his influence to have him released from custody and tells him that Dexter is the only person who knows Freebo's location. King then kidnaps Dexter and prepares to torture him, but Dexter manages to break free and kill him
- Co. Sheriff Ramon Prado, Miguel's other brother, is the main secondary antagonist. After Oscar's death, Ramon becomes obsessed with finding Freebo. He criticizes Miami Metro Homicide for not doing their job, but mainly antagonizes Dexter for his new friendship with Miguel. After he is found torturing a suspect for information on Freebo, Ramon is forced out of the Sheriff's Department on early retirement. After Miguel's death, Ramon attempts to kill Dexter in public, but fails and is taken into custody. He later realizes that all his anger is towards Miguel; now that his brother is dead, Ramon is free. As one last favor to the Prado family, Ramon is released.
- Freebo may also be considered one of the main secondary antagonists, since he was instrumental in the main antagonists being involved in the storyline.
- Arthur Mitchell, also known as The Trinity Killer, is the main antagonist. After discovering that Mitchell has a family and has successfully lived a dual life for more than thirty years as an active serial killer, Dexter tries to befriend him in an effort to learn how he does it. Though he knows the risk Mitchell poses, Dexter lets him live on several occasions, even going as far as to stop Mitchell from committing suicide, because he thinks he can learn from him. Eventually, however, Dexter discovers that Mitchell's "happy" home life is a sham, and his wife and children are actually terrified of the mentally and emotionally unstable Mitchell. Mitchell figures out Dexter's deception and, believing Dexter is only trying to extort him, threatens to destroy Dexter's life if he doesn't leave him alone. Dexter eventually manages to trap and kill Mitchell, but not before Mitchell made good on his promise—after disposing of Mitchell's remains, Dexter comes home to find his wife Rita dead as Mitchell's final victim. Arthur visits Miami Metro using a stolen "visitor" tag, to investigate Dexter.
- Christine Hill, a reporter and Arthur Mitchell's first daughter, is the main secondary antagonist. She begins dating Joey Quinn to keep tabs on the police and find out how close they are to catching her father. Christine has major daddy issues, willing to do anything to make Arthur love her, but is shut out by him at every chance. When Frank Lundy gets close to figuring out Trinity's identity, Christine kills Lundy and injures Debra Morgan, making it look like a shooting by the Vacation Murderers. After Christine lets a private detail of the crime slip while talking to Deb, Miami Metro finds out she killed Lundy and that she's Trinity's daughter. Ultimately, she commits suicide after Arthur abandons her and Debra refuses to forgive her.
- Vacation Murderers, Johnny Rose and Nikki Wald, are also secondary antagonists, the investigation into their crimes being a primary focus of LaGuerta and Batista's subplot. LaGuerta and Batista go to Nikki's house, where she and Johnny open fire on them and escape. They are later blamed for Christine Hill's shooting, and Batista runs a story revealing Johnny's status as a carrier of syphillis. When Nikki reads this, she argues with Johnny and ends up killing him. Taken into custody, Nikki confesses to every crime she committed but not the Lundy shooting, for which Miami Metro later realizes they were not responsible.
- Jordan Chase is a famous author and motivational speaker, as well as the leader of the Barrel Girl Gang, a group of sadistic men responsible for abducting, raping, and killing several women. Dexter ends up saving their thirteenth known victim, Lumen Pierce, from death, after which the two team up and hunt down the group's members one by one. Eventually, Chase is the only one left, and abducts Lumen to set up a trap for Dexter. But when Dexter finds them, he manages to gain the upper hand, and Lumen stabs Chase in the heart.
- Stan Liddy, a corrupt narcotics officer is meanwhile busted in a sting operation. He is later released from custody but suspended from the force. Joey Quinn approaches Liddy to look into Dexter, whom Quinn suspects of involvement with Arthur Mitchell. Liddy finds evidence of Dexter's dark secret, and becomes obsessed with exposing him to restore his own reputation, dogging him even after Quinn stops supporting the investigation. Liddy eventually kidnaps Dexter and tries to extort a confession from him, but Dexter overpowers and stabs Liddy.
- Carlos and Marco Fuentes (Santa Muerte Case) are also secondary antagonists, as Debra investigates their crimes. Carlos ultimately ends up being Debra's first kill.
- Travis Marshall, a.k.a. The Doomsday Killer.( Professor James Gellar is initially thought to be working with Travis, but he is found dead, later revealed to have been murdered by Travis approximately three years before the season started.) Travis is the first antagonist to have a Dark Passenger appear in physical form, and the second character overall (Dexter Morgan being the first). His Dark Passenger manifests itself as Gellar. Under the guidance of "Gellar," Travis kills several people and stages their bodies in public tableaux alluding to the Book of Revelation, his goal being to bring about the end of the world. Travis later tries to resist his murderous side, but his Dark Passenger eventually overtakes him and he continues his delusional mission without the Gellar manifestation. He tries to carry out his plan's final phase by murdering Harrison Morgan, but Dexter stops and kills him.
- Professor James Gellar is the biggest secondary antagonist of the season. Until he is revealed to be a hallucination, Gellar is believed to be a second (and more dominant) Doomsday Killer, serving as Travis' mentor, until Travis remembers that he actually killed the real Gellar long ago. As the dark side to Travis' split personality, Gellar personifies the evil in him for the first three-quarters of the season.
- Dexter's darkness as Brian Moser appears in the episodes "Just Let Go" and "Nebraska". After "avenging" Brother Sam's death, Dexter convinces himself there is "no light" in him, and "Brian" appears to guide him down a darker path. In "Nebraska," Brian tries to tempt Dexter into giving up the code and becoming a reckless killer, but Dexter eventually re-accepts Harry and his Code.
- Steve and Beth Dorsey are recruited by Travis Marshall late in the season. They assist in the murder of Holly Benson and the creation of The Wormwood tableau.
- Louis Greene also starts to become an antagonist near the end of the season, when it is revealed that he bought the Prosthetic Hand from Ryan Chambers. He somewhat idolizes Dexter until the latter harshly criticizes the game that Louis created - Homicidal Tendencies. Louis later ships the hand to Dexter's apartment to mess with him.
- The Locos street gang members are in conflict with Brother Sam when he tries to reform Nick, a former member. Dexter kills the gang's leader, Julio Benes, while their lieutenant, Leo Hernandez, is gunned down by Miami Metro. After Nick kills Sam, Dexter drowns Nick in the sea.
- Isaak Sirko is the leader of the Koshka Brotherhood, a Ukrainian-based crime syndicate responsible for the deaths of numerous people, including but not limited to Kaja Soroka, Mike Anderson, Tony Rush, Alex Dubrozny, Andres Rodriguez, and two unnamed Colombians. Isaak comes to Miami after Viktor Baskov, who is later revealed to be his lover, fails to make his flight back to Kiev. He leaves a trail of bodies in search for Viktor, and eventually learns that Dexter killed Viktor. Dexter tries to have Isaak killed through the Brotherhood's Colombian rivals, but underestimates Isaak's skills as he kills all the assassins with ease. Isaak is arrested for the murders but later released due to evidence tampering by Joey Quinn at the behest of George Novikov. Isaak and Dexter form a complicated relationship, as Dexter learns the truth behind Isaak's desire to kill him, while Isaak believes he and Dexter could have been good friends under different circumstances. When the Brotherhood turns against Isaak and sends assassins after him, Isaak forces Dexter to help him by kidnapping Dexter's girlfriend, Hannah McKay. Isaak promises to leave Dexter alone after it's done. The two work together to dispatch the assassins, but George then appears and shoots Isaak himself. As a last request, Dexter takes Isaak to the spot where he dumped Viktor's body, and Isaak gives Dexter one last piece of advice about love before dying. Isaak appears in Miami Metro after he is arrested to be questioned about the murder of the Colombians.
- Captain Maria LaGuerta, who never fully believed that James Doakes was The Bay Harbor Butcher, finds a blood slide at Travis Marshall's crime scene and determines that the real Butcher (Dexter) is still at large. She privately investigates and begins to suspect Dexter when she finds his name on a list of boat owners. She enlists the help of Thomas Matthews, who doesn't believe her theory but agrees in exchange for his full pension. They go to the Everglades site where Doakes died and learn that the cabin was being rented by Santos Jimenez, one of the men who killed Dexter's mother, Laura Moser. LaGuerta then baits Dexter by pulling strings to have prisoner Hector Estrada, the man who ordered Laura's death, released on parole. Dexter goes after Estrada, but stops after realizing LaGuerta has put a tail on Estrada. Dexter later manipulates evidence to discredit LaGuerta with the department, but she perseveres and finds evidence that Debra is helping Dexter's criminal activities. Dexter then sets a trap for LaGuerta by capturing Estrada and luring her to a meeting with him. Dexter injects her with M99 in order to frame her for killing Estrada and vice-versa. When Deb appears, LaGuerta comes to and tells Deb to shoot Dexter. However, Deb ends up shooting Maria herself. Horrified, Deb grabs her body in tears. LaGuerta works at Miami Metro all the time.
- Viktor Baskov, George Novikov, Jurg Yeliashkevych, Oleg Mickic, and Benjamin Caffrey are all secondary antagonists this season, as all of them members of the Koshka Brotherhood. Viktor, who kills Mike Anderson, is the first member of the Brotherhood to appear in the season, and is killed by Dexter. His death can be seen as an incentive for much of the season's conflict, as his death motivates Isaak's mission in the first place. Novikov also has a subplot as an antagonist to Joey Quinn, using Quinn's girlfriend Nadia, who is owned by the Koshka Brotherhood, as leverage to force Quinn to assist in the Brotherhood's operations.
- Hannah McKay is also a secondary antagonist for a completely different reason. Dexter initially plans to kill her, but changes his mind and instead begins a romantic relationship with her. After Hannah poisons Sal Price, Debra antagonizes her and begins working to arrest her. Hannah eventually tries to stop Deb by drugging her water; after Deb crashes her car, Dexter finds evidence of foul play and betrays Hannah to the police. However, with help from Arlene Shram, Hannah manages to escape police custody and go on the run.
- Louis Greene's inner nature becomes more apparent, as he steals Dexter's credit card numbers and cancels them. After Dexter breaks into his apartment and investigates why Louis sent him the hand, he finds his credit card numbers, a video of Louis receiving oral sex from a hooker, and evidence that Louis planted child pornography on his partner Robert Henley's computer, having him arrested by the FBI. When confronted, Louis confesses that it's retaliation for Dexter criticizing his game. Dexter tells Louis to get out of his life, but Louis doesn't back down. Dexter considers killing him, but instead sends evidence of Louis' offenses to two people with whom he has close relationships: his boss Vince Masuka and his girlfriend Jamie Batista. He anonymously mails the hand to Vince and the hooker video to Jamie, getting Louis both fired and dumped. Louis tries to sink Dexter's boat in revenge, but is caught and interrogated by Isaak Sirko. After Louis reveals Dexter's name, Isaak kills him.
- Ray Speltzer is a serial killer who kidnaps and tortures women by chasing them through elaborate labyrinths, wearing a bullhorn helmet, and brutally beats them to death, taking their earrings as trophies. He attempts to kill Debra Morgan and also traps Dexter in his most elaborate labyrinth, only for him to escape. Dexter later kills Speltzer, putting his body in a crematorium.
- Sal Price, an investigative journalist and true crime author, covers the Hannah McKay Case, and becomes romantically interested in Debra Morgan, whom he assists in the investigation. When Price discovers the relationship between Dexter and Hannah, he tries to blackmail Dexter into giving him info about Wayne Randall's last moments. In order to keep Price from publishing information about Hannah, Dexter deletes Price's files and threatens to release false evidence implicating Price in a murder he previously reported on. However, Price is poisoned by Hannah before Dexter can put his plan into effect, and dies in Dexter's apartment.
- Joe Jensen, a.k.a. The Phantom Arsonist, burns people alive. He is nearly killed by Dexter, but Dexter allows him to live at the last minute and leaves him for the police to find.
- Oliver Saxon, a.k.a. The Brain Surgeon, is the main antagonist of Season Eight. His identity is unknown for most of the season and presumed to be a former patient of Evelyn Vogel. But he is later revealed to be her son, Daniel Vogel, having faked his death and changed his name years ago.
- Jacob Elway is the second main antagonist of Season Eight. He is the owner of Elway Investigations, a private business. Originally Debra's kind employer, however, after learning that Hannah McKay is back in Miami, he pursues her relentlessly and as a result threatens Dexter, Harrison and Debra's future.
- Javier Guzman, a.k.a. El Sapo, is a hitman who targets Andrew Briggs, who robbed a jewelry store owned by his employers. This leads to his encounter with Debra Morgan and his death.
- A.J. Yates was a serial killer who abducted women and kept their shoes as trophies. Dexter suspected him asThe Brain Surgeon because of a surgical scar on his head, and attempts to kill him, but Yates escapes and later kidnaps Evelyn Vogel. Dexter is able to find them and kill Yates.
- Zach Hamilton was a personal antagonist to Joey Quinn, who suspected him of murdering Norma Rivera and Cassie Jollenston.
- Deputy Marshal Max Clayton comes to Miami to look for Hannah McKay, who is believed to be back in town. He eventually learns that Debra may secretly know Hannah's whereabouts, and follows her. However, he ends up crossing paths with Oliver Saxon, who kills him.
A few antagonists are featured in more then one season, which makes their status as antagonists a little bit unclear:
- Juan Ryness - Despite only being seen and referenced in flashbacks and dream sequences (and never seen alive) he can be considered the only antagonist Harry Morgan ever had in the series, being essential to Dexter's early life.
- Frank Lundy - FBI Special Agent who hunts The Bay Harbor Butcher in Season Two and The Trinity Killer in Season Four. He can be considered a main antagonist in both seasons but he's written out as a secondary one. Lundy temporarily works at Miami Metro in Season 2 and is a prominent visitor in Season Four.
Early Cuts: Season One
- Alex Timmons, Gene Marshall, and Cindy Landon are main antagonists in the first season, which focuses on Dexter's attempts to kill them.
Early Cuts: Season Two
- Peter Thornton is a young student and serial killer who mimics Dexter Morgan's style.
- Robert Milson is an associate criminology professor in criminal justice and a serial killer who killed eight people.
- Jenna Lincoln is a girl who is responsible for three deaths. She becomes a target of Dexter.
Early Cuts: Season Three
- Coleman Lindquist and Max Lindquist are main antagonists of this season. They are a father/son team of killers responsible for a string of murders of prostitutes and their johns.
Darkly Dreaming Dexter
- Brian Moser (Novels) is a serial killer dubbed the "Tamiami Slasher." He rampages through the city and begins sending messages to Dexter.
Dearly Devoted Dexter
- Dr. Danco is a serial mutilator who tortures his victims by cutting off every part of their body that isn't vital to life. This leaves them unable to move or communicate, driving them insane.
- Sergeant Doakes is an antagonist towards Dexter, though not in the same manner as Dr. Danco, Doakes pushes Dexter to a corner, metaphorically speaking, as Dexter is forced to hide behind a mask (Rita and the kids) to avoid been caught infraganti by Doakes who stalks him for the most part of the novel.
- Steve Reiker - Dexter is unable to kill him for a long time because of Doakes.
Dexter in the Dark
- Moloch is the original Dark Passenger. He is a deity worshiped by the Cult of Moloch, which kidnaps Astor and Cody.
Dexter by Design
- Brandon Weiss, a fired writer from The Greater Miami Convention and Visitor's Bureau snaps from stealing corpses and making art objects out of them to direct killing, after Dexter mistakenly kills his lover Alex Doncevic. Knowing that Dexter is a killer, he eventually tries to reveal this.
- Doakes, despite having his feet, hands and tongue cut by Dr. Danco continues to suspect Dexter. His suspicion eventually makes Detective Coulter another antagonist.
Dexter is Delicious
- The Coven, a group of cannibals.
- Brian returns, but becomes an ally.
- Bernard Elan, a copycat killer of Dexter's.
Dexter's Final Cut
- Robert Chase, a pedophile serial killer targeting Dexter's family.
Dexter is Dead
- Raul, head of a Mexican drug cartel.
Dexter 2013 Volume
Dexter is a five-issue limited series comic book written by Jeff Lindsay, painted by Dalibor Talajic and published by Marvel Comics in 2013. It is based on the popular Dexter novels written by Jeff Lindsay.
- Steve Gonzalez is a millionaire philanthropist, the Mother Teresa of Miami as referred by several people in Miami. Though Debra initially does not suspect about Steve, his past with a young Dexter allows Dexter to detect Gonzalez is just using his public image as a mask. Gonzalez is actually killing anyone who might endanger his plans, and is also enslaving people in an island where he will built a complex known as Mar Dorado.