Lieutenant Eve Dallas: He likes it. Sometimes evils its own root.
Mira: I want to disagree. The reasons, the whys of abnormal behavior are important to me. But I have no reasons, no whys, for David Palmer.
NYPSD Lieutenant Eve Dallas, Roarke, and their allies have faced dozens of serial killers and other murderers. A select few are especially vicious.
- Ceremony in Death: Selina Cross and her lover Alban run the Church of Satan where they routinely conduct Human Sacrifice, including of children. Adhering to a sadomasochistic dogma, the two sexually abuse their parishioners regularly, including an approximately 17- or 18-year-old named Alice Lingstrom who eventually flees them after she witness a child sacrifice. The two murder her grandfather and frighten Alice to get fatally hit by traffic; murder followers for talking to Eve; and seduce and drug at least one adherent of the benevolent Wiccan Isis Paige to act as their pawns and proxies to murder in their stead, while framing Isis's lover for at least a couple of murders. Alban eventually kills Selina, before revealing that, while she actually believes in Satan, he is only using the Church as a long con; he then prepares to drug Eve so she'll be forced to enjoy it when he rapes her.
- "Midnight in Death" novella: David "Dave" Palmer is an intelligent murderer who seeks to understand how people are affected by pain for both his intellectual curiosity and personal enjoyment. To this end, Palmer kidnaps people and tortures them to near-death before reviving them with his electrical torture system and then repeating the process over and over again until he kills them, often by slow strangulation. Three years prior, after having killed eight people, Palmer was sent to prison by Eve, and upon escaping swears revenge against her and the others at his trial. Palmer takes Eve's friend, NYPSD profiler Dr. Charlotte Mira, hostage, only letting her go when Eve offers to take her place in Palmer's electrified cage.
- Conspiracy in Death: Dr. Michael Waverly, the head of the AMA (American Medical Association), murdered one of his fellow doctors to ensure that his lifesaving organ transplant system for the poor could not be implemented. Viewing himself as a god, Waverly, with the assistance of other doctors, experiments on the homeless for his new organ repair research before killing them by cutting out said organ; in one case, the woman was butchered to the point of bleeding to death. When the police begin to investigate, Waverly threatens the lives of the pregnant wife and five-year-old son of one of the policemen, and when Eve is sent to investigate, arranges to have her mentally destroyed by framing her for the murder of a rival of hers, who he had killed himself. When Eve gets close to the truth, Waverly starts to kill off anyone who could implicate him, including fellow conspirators and his friend's niece. During the final confrontation with Eve, Waverly declares his intent to take over the organ transplant system and purge the world of the poor and downtrodden, who he views as "dregs". For all his talk about helping people, Waverly really only cares about "glory, fame, wealth, power".
- Betrayal in Death: Sylvester "Sly" Yost is a hitman who, while his estimated fee of approximately $2 million per hit, plus expenses, allows him to indulge a "refined and cultured taste", is utterly ruthless and vicious; Yost is believed to be responsible for over 40 hits. Yost's MO is to beat the victim, then rape the victim—regardless of gender—before finally strangling them with a two-foot-long silver wire. Yost then takes a souvenir from the victim. Yost, hired to distract Roarke so hundreds of millions of dollars of items that Roarke's company is managing the auction of can be stolen, starts by killing a housekeeper at one of Roarke's hotels, then killing another employee who's also a friend of Roarke. Yost then attempted to kill Summerset; plans on killing Roarke himself—which would result in a bonus of $25 million—and then plans to kill Eve for free.
- Imitation in Death: Niles Renquist is a misogynistic sociopath who so chafes under how he believes women oppress him that he turns to serial murder as an outlet, attacking women to mimic his idols' MO. Sexually abusing his maid while loathing his wife and daughter, Renquist adopts the personas of past serial killers, including Jack the Ripper; Albert "The Boston Strangler" DeSalvo, using a broomstick to sexually assault his victim before killing her; and Ted Bundy. After killing multiple women, he plans to emulate a serial killer to torture and rape his victims, carving them into pieces while they are still alive, with Eve speculating he would have eventually killed his own wife and young daughter.
- Origin in Death: Dr. Jonah Delecourt Wilson is an egomaniacal scientist whose evil spans decades, even going back to the Urban Wars era, in his quest to reshape humanity to his will. Along with the more sympathetic Dr. Wilfred B. Icove Sr., Jonah used the DNA of deceased Urban Wars era orphan girls in order to illegally clone them and then mold them into prostitutes, soldiers, spies, like Deena Flavia, or various other purposes for willing buyers or using them as forced incubators for his latest clones. After Deena begins to take out the leaders of his organization, including Icove himself, Wilson is revived as a clone himself along with Icove who he promptly murders for having second thoughts. Wilson—who uses presumably cloned boys as disposable soldiers—kidnaps Deena's baby daughter and uses her as a hostage before deciding to blow up the cloning facility with every child in it out of spite at being denied victory.
- Innocent in Death: Rayleen Straffo is an adorable 10-year-old sociopath who, at the age of 7, because she was jealous of him getting all the attention, shoved her brother, who was almost two years old, down the stairs, fatally breaking his neck. Rayleen later murdered an old woman for fun, before using ricin to poison her kindly teacher for giving her an A- on an assignment, melting his organs in an excruciating death, and intentionally traumatizing her best friend as a result. Killing another teacher to pin it on her school's principal—who Rayleen felt was too strict—Rayleen eventually poisons her own mother, trying to kill her, due to viewing her as weak and to use her as a scapegoat for her murders, making her one of the youngest, but no less vile, killers of the series.
- Creation in Death: Robert Lowell is a genial man who is also "The Groom", a vicious serial killer who is believed to be responsible for the deaths—his "gift"—of well over 20 women, who he considers "partners". Decades ago, The Groom overheard his stepmother, opera singer Edwina Spring—whom he supposedly loved—plan to run away with a soldier, and so made his father James and his grandfather, also named Robert, believe she was a spy, at which point they tortured her. Having learned the art of torture from his grandfather, The Groom's MO is to trick a woman—one he has studied for weeks if not months—who physically resembles his stepmother, then brutally torture them using various implements—while listening to opera and enjoying the screams—until he grows bored, at which point he slits the victim's wrists and lets them bleed out. The Groom then carves how long they survived into their torso and puts a ring on the corpse's finger, before dumping the body where it will be seen. The Groom eventuality tranquilizes Eve and plans to make her his greatest victim before he self-terminates.
- New York to Dallas: Isaac McQueen, aka the Collector, is a pedophile responsible for the torture—including tattooing a heart with each victim's number on each victim's chest—and rape of over 25 girls and teenagers ages 12 to 15—his "bad girls"—as well as the possible murder of 4 of them, in New York alone, and the torture, rape, and possible selling of others prior. McQueen also works with older women—"Mommy" figures, similar to his own abusive mom who was his first partner and who he killed when he was 19—seducing them and slashing their throat with a knife when they are of no more value to him. Escaping from prison, McQueen murders a medic and later assaults and rapes a woman as well to get Eve's attention, wanting revenge on her for putting him away a dozen years prior. Teaming up with Eve's mother, McQueen kidnaps a young teenager named Darlie Morgansten, raping her and forcing her to scream for Eve's help; he then murders Eve's mother—who didn't recognize Eve—for getting caught. McQueen later attacks Eve, planning to rape and kill her.
- Delusion in Death: Lewis "Lew" Callaway is a mid-level marketing executive who ends up with one of the highest body counts in the entire series. An Attention Whore envious of his coworkers, Callaway, with the help of his equally evil grandmother, uses Wrath of God, a formula from his Urban Wars-era terrorist grandfather, to have nearly 130 people kill each other in two separate attacks, all just to get rid of two coworkers. He also admits to have been planning a third attack.
- Thankless in Death: Jerald "Jerry" Reinhold snaps one day and brutally kills both his parents when they threaten to kick him out of their apartment. Jerry next kills his ex-girlfriend, and then tortures and kills a former teacher—after injuring her dog. Jerry makes a "Shit List" of anyone who he views to have even slightly offended him, planning to subject them to torture and gruesome murders, after which he plans to rent out his murder talents for any paying customers. Jerry next brutally tortures and tries to kill his best friend. A complete egotist who refuses to accept any responsibility for anything he's done, Jerry is completely happy to bask in the wave of attention his murders receive.
- Apprentice in Death: Willow "Will" Mackie, a 15-year-old who loves being the center of attention, is responsible for 25 deaths and scores more wounded. Willow's father, former NYPSD sniper Reginald Mackie, is distraught and starts taking drugs when his second wife, Willow's stepmother, is killed in an accident. Willow, supposedly to help her father but really because she thrives on attention, formulates a plan whereby the Mackies target those supposedly responsible for his ex's death. With Reginald having trained her and assisting, Willow uses a laser rifle to first kill 3 people including a target, the latter painfully shot in the gut; then 4 people including a second target, with a fifth victim wounded; and then, even after Reginald was captured, Willow by herself executes a mass shooting at Madison Square Garden, killing 18 people including a third target, and wounding dozens. Willow's cruelty isn't limited to the sniping, as she torments—and eventually plans to kill—her stepfather, own mother, and 7-year-old half-brother, whose dog she had killed. Willow has others she plans to kill, and eventually plans to hit her high school and kill at least 100 there and in the surrounding area, making history.
- Golden in Death: Stephen "Steve" Whitt is a selfish man who enacts a particularly cruel Revenge by Proxy scheme. When his ex-girlfriend gets engaged, Whitt, who Eve says feels like "she belonged to" him, uses a nerve agent to kill the loved ones of those he holds responsible for his getting removed from the elite high school academy he was enrolled in, where he was a bully—and worse; he knows those people will live, but will suffer. Whitt and his friend Marshall Cosner have 7 targets, and 2 are killed, while a third delivery of the gas is intercepted. Whitt also fatally stabs the person who came up with the formula; uses the formula to kill Cosner when the latter becomes a burden; plans to eventually sell the formula; and even threatens to kill his own attorney's wife.
- Faithless in Death: "Reverend" Stanton Wilkey is the utterly vile leader of the Natural Order, a racist, ultraconservative cult that teaches the "place" of women and children. A depraved tyrant with a god complex, Wilkey and the order have for decades had many women abducted and tortured to make them submissive "brides" the Natural Order can sell off to adherent politicians, celebrities, and judges as wives as breeding stock, with rape and forced impregnation being common; the babies are also bought and sold. Gay children and teenagers of the cult are subjected to torture and potentially sterilized, with Wilkey also having women kidnapped for him to rape as "breeding wives" of his own.
- Desperation in Death: Jonah K. Devereaux is the wealthy head of Reliable Delivery Services, as well as the brains and money behind a vile, massive Human Trafficking ring. "The Pleasure Academy" takes women and girls, with the latter as young as 11, if not younger, and grooms them—via drugs, electric shocks, and other methods—to become domestic slaves and sex slaves; the Academy also produces videos featuring its victims. In addition, the Academy occasionally holds auctions in which the girls are sold; in the most recent auction, Devereaux is even double-crossing his otherwise equally-vile partner, "Auntie" Iris Beaty, aka Iris Swan, who runs the Academy's day-to-day operations and considers Devereaux a friend. Devereaux also has his own sex slaves, and in fact is killed by his newest one after he tells her how he plans to share her with his friends.