Karl Arnold, aka The Fox, is the first "family annihilator" to appear in the show, and the only one to put in more than one appearance. Debuting in "The Fox", Arnold uses his position as a family psychiatrist to seek out families that he feels are dysfunctional (that is, where the father is not the dominant personality), stalks them, and then kidnaps them while the neighbours believe them to be on vacation, using his control over the children to keep the parents hostage. He keeps them separated from one another for days, then brings them together for one last supper, after which The Fox marches the entire family into the basement and kills them, starting with the children and ending with the father. Upon his capture, The Fox explains that he does this because his own family fell apart due to his obsessive-compulsive, controlling nature, and he wants to show how much worse things can get when the head of the household isn't "strong". At this point, it's still possible for the viewer to have sympathy for Arnold, due to the fact that the episode focuses on his OCD and the fact that he's having a mental breakdown. This does not hold true in "Outfoxed", his second appearance. Interviewed by the FBI for help with another family annihilator, Arnold comes off as calm and in control, repeatedly asking to see pictures of the crime scenes, coming onto Prentiss, taunting Hotch for his marital problems, and gloating about the fact that before he killed the families he took hostage, he would beat the male children, and rape the female ones. This revelation, coupled with The Fox's smug, superior demeanour, and the fact that he's become penpals with The Boston Reaper (laughing as he tells Hotch that The Reaper is coming for he and his family) wipes out any sympathy the viewer might once have held, and puts him firmly in this trope.
Charles Holcombe from "Legacy". He views homeless people as subhuman specimen who should be exterminated. So he kidnaps them and brings them to his torture chamber, where he puts them through agonizing physical and mental torment before dissecting them alive. And he's been doing it for a very long time. He even gives them the opportunity to escape by telling them they can leave if they make it out in a certain amount of time (and if they manage to do it, he knocks them out with gas to avoid their escape). In the end, he is shot and killed by the BAU and one only wishes he had suffered more. Also, his last words? "Just let me do my job!" Irrepentant, smug, and cruel until the very end.
As one of the show's few recurring villains, George Foyet, aka The Boston Reaper, had ample time to establish his monster credentials. Dissappearing after a long, unsolved killing spree, The Reaper comes out of retirement following the death of Tom Shaunessey, the lead investigator from the original case. Killing two couples, The Reaper baits the BAU into entering the case, then calls up Aaron Hotchner (for whom his original spree was That One Case), offering to stop the killings if Hotchner admits defeat and calls off the investigation—the same deal that The Reaper had cut with Shaunessey years ago. When Hotchner turns him down, The Reaper massacres an entire bus full of passengers. He later kidnaps a journalist who had written a book about him and demands the man correct the errors in it (most notably suggesting that The Reaper might have died rather than retired); when Hotchner captures him, The Reaper reveals that he's done it all in order to be "more famous than they'll ever realise." Breaking out of jail, The Reaper bides his time before ambushing Hotchner at home, where he tortures him, than drops him off at the hospital, along with clues that indicate he is going after Hotchner's ex-wife, Hayley, and son, Jack. Mutilating and mortally wounding the officer assigned to protect them, he tracks Hayley and Jack to their home, murders Hayley while forcing her to talk to Hotchner over the phone, and then gloats to the BAU Agent's face that after he's done with Hotchner, Jack will be next. Totally self-centred, driven by an obsessive desire for fame and control, and needing a nemesis in order to function properly, The Reaper is Aaron Hotchner's personal nightmare.
"Mosley Lane" gives us Anita Roycewood, a serial kidnapper and child murderer, who forces her submissive husband, Roger, and first kidnap victim, Charlie Hillridge to help her abduct and imprison children. Keeping the children locked up in a hidden hallway, Anita renames them, dyes their hair, and is implied to sexually abuse them, using fear, beatings, and threats to the other children to keep them in line. When the children grow too old for her liking, or become uncontrollable, Anita knocks them out (in the case of Steven Shepherd beating him savagely beforehand), places them in a cardboard box, and burns them alive in a crematorium, whistling jauntily the entire time. When the police catch onto her, Anita abandons Roger, and takes the three remaining children, Aimee Lynch, Mae Hall, and Charlie to the crematorium, where she tries to force Charlie to help her burn the other two; she then intends to kill him. Guilty of some of the most callous crimes yet shown on the show, and viewing her victims as replaceable, Anita's reasons for doing what she does are never explored, leaving only an utterly hateful cipher for the cast and the audience to deal with.
DeputyRonald Boyd from "A Rite of Passage". Profiled as a "human predator", Boyd kills illegal immigrants because it allows him to assert a sense of power that he otherwise lacks. He lies in wait at border crossings, picks out a straggler, and then chases them through the desert on his ATV until they can no longer fight back, finishing them off with his machete. When the Hispanic sherriff (whom he loathes for being new to town) starts looking into the missing illegals he sends her progressively more aggressive "messages" - severed headsin boxes outside the sheriff's office, a severed head on a pole in her front yard - until he finally kills her for sticking her nose into his business, while ranting that the illegals aren't really missing because "they ain't supposed to be here in the first place." Dismembering her corpse in order to pin the blame on drug kingpin Omar Morales, Boyd proceeds to murder Morales and most of his gang to cover his tracks (also they're Hispanic too). When his partner objects, Boyd shoots him and places the gun in the hands of the dead Morales. Taking offense to the idea that he sees himself as weak, and viewing himself as a total badass, Boyd is an unrepentant SOB with no Freudian Excuse, who makes your average Dirty Cop look like an angel.
James Stanworth from "25 to Life". Not only did he stab Carrie Sanderson and her little daughter Abby to death, but also managed to place the blame on Donald Sanderson, sending him to jail. He also killed another woman to satisfy his psychopathic urges that he couldn't manage to keep hidden anymore. Unluckily for him, this last murder puts the BAU on his tracks. He's also implied to be a Corrupt Corporate Executive and is trying to become a corrupt politician. He's heavily hinted to be well-connected enough to have gotten away with everything...if only he hadn't committed the third murder.
"Proof" gives us Benjamin "Cy" Bradstone, whose mental disability makes him unique, but not even slightly sympathetic. Pretending to be far more handicapped than he is, Cy lures women out of the public eye, forces them into his shed, rapes them, uses sulfuric acid to burn away their senses, and then stabs them to death. If they don't like the way he looks, he takes their eyes. If they spit when he kisses them, he takes their sense of taste. If they don't like his smell, he burns out their nostrils. His video journal reveals that he has been like this since he was a young boy, and he gloats that he brutalizes women for the same reason that he used to beat his dog: because it's fun. We eventually discover that he is targeting women who remind him of his sister-in-law, whom he attempted to molest when they were both teenagers. When his niece puts on a cheerleader costume that reminds him of her mother she becomes Cy's final victim. After his arrest, his brother Matt (who has always been supportive of Cy, going so far as to offer to let him move in with him) demands to know why Cy did this; Cy laughs in his face, and tells him that he has always hated Matt and was planning to deafen and then kill him one day. A ragingly misogynistic psychopath who just happens to be handicapped, Cy is fully aware of how awful his actions are, as evidenced by this message he leaves for Matt:
"What I'm going to do to your daughter, you can see on this tape. But what I did to your wife? Now that's a video you should see."
Clark Preston from "A Thin Line", a crooked real estate developer who hires crooks to commit crimes in neighborhoods so people will leave them and he can buy up their property dirt-cheap, not caring about who gets hurt in the slightest. He only gets worse from there. He starts a mayoral campaign, having his faithful toady murder entire families (including a baby in one case) and pin it on innocent black and Hispanic people to add fuel to his blatantly racist campaign platform. Fortunately, unlike a lot of wealthy perps on this sort of show, who use their resources to expertly cover their tracks and pull a Karma Houdini, he was dumb enough to use an ordinary phone to relay his orders to his toady, allowing the FBI to get him in the end.