Since Saxon and Chase have been brought here, I thought I'd knockout the last candidate from the show itself. There is another one from the Dexter prequel webseries, which I or someone else can nominate later, but as for the show itself, this is the last qualifier.
What is the work?
Dexter is a tv series based on a series of novels about a vigilante serial killer of murderers named Dexter Morgan. The show is recently going to be renewed for one more season.
Who is King and what does he do?
George King is one of the two primary antagonists of season 3. He is a former torturer who became infamous and feared for his horrible methods during war; he interrogated enemy soldiers while slowly skinning them alive (I'm pretty sure that's illegal even in times of war. I don't think you are allowed to slowly torture prisoners to death for information, correct me if I am wrong). After the war, he moved to Miami and started a tree trimming company. He had his name changed from his birth name of Jorge Orozco. While running his company, he was very controlling and ruthless with his workers, to the point they feared him. After loaning money to Freebo, a drug dealer and murderer who failed to pay him back, King became furious that someone had apparently cheated him, and went on a rampage to get the money back.
In search of Freebo, King kidnapped the man's girlfriend and took out his old torture tools, slowly skinning her alive while interrogating her for information on Freebo's whereabouts. After gaining whatever information he could from her, he killed her by strangulation, leaving her body in the open. After Freebo was killed by Dexter Morgan, King, still unable to find the man and collect his money, kidnaped the pimp friend of Freebo who introduced him to the prostitute who later became his girlfriend. As before, he tortured the pimp for information by skinning him alive, strangling him to death after it became obvious the man had no useful information. After Debra Morgan begins talking with a 14 year old boy for information to help with the "Skinner" case, King kidnaps the boy and slowly kills him by skinning him alive. Unlike the other victims, the boy isn't questioned by King, who knew the boy was of no use. King simply wanted to punish the boy for helping the police with the investigation. Also unlike the other people King killed, the boy dies from the skinning itself. King proceeds to leave the body in the open to serve as a message to everyone: Don't help the police with the Skinner case or the Skinner will do this to you. The police eventually deduce that the Skinner is finding his victims by spying on them while cutting trees. They find King cutting trees outside the home of one of the victims and confront him. To try and protect himself, King denies being involved and cooperates with them, acting like a friendly man and even providing a list of all his employees so the police can look into them for suspects. King tries to make one of his employees a fall guy, revealing that his employee Mario, who conveniently was the one who originally discovered the body of the pimp, stabbed a man years ago, throwing him under the bus and trying to frame him for the killings. The police however deduce that Mario is not the killer. King goes on to capture Anton Briggs, believing he knows Freebo's location. King makes the skinning much worse than the previous ones, going much slower and dragging it out. Anton is saved by Debra and Joey Quinn when they arrive on the scene, although King escapes and leaves Quinn injured.
Miguel Prado misleads King into believing Dexter knows the location of Freebo, though this was done simply so King would kill Dexter. King takes Dexter to his hideout where Dexter reveals that he killed Freebo. It is here that Dexter deduces that King greatly enjoys reliving his torture days and that the search for the missing money he was owed only made a convenient excuse. His primary reason for his killings was not actually about the money (which even if it was, it was by no means a sympathetic motive anyway), it was simply because he liked torturing and killing people. The search for Freebo and his money simply gave him a pattern for selecting victims. King appears faltered at first hearing that Freebo is dead, but quickly turns back around and claims he doesn't believe Dexter, to which Dexter concludes that King does in fact believe that he is dead and is simply lying to himself to continue and give himself an excuse to skin Dexter. King leaves to get his torture tools as Dexter frees himself and turns the tables on King, breaking his neck and killing him.
Freudian Excuse/Mitigating Factors?
He claims that he wants his money. Obviously this does not at all justify the horrible lengths he is willing to go to in search of Freebo. Furthermore, it is made clear that King didn't even really care about the money and simply felt that he was being disrespected. He was willing to skin people alive in search of a man who he felt had disrespected him. That speaks volumes about how narcissistic he was, which is further shown in how demanding and controlling he was toward his employees. Dexter concludes that all this was only a secondary goal; he really wanted to relive his experiences of torturing and killing people in the army. Defending his honor and reputation was simply a bonus that also gave him a convenient excuse and pattern of selecting victims.
The Dexter series is filled with killers. Jordan Chase and Oliver Saxon are proof of how nasty things can get. That being said, while King may not be a rapist, be the foe who caused the most personal harm to Dexter, or have the highest bodycount, one area where he truly does excel is his methods. He is the most torturous of the killers in the series, slowly skinning his victims alive. No other killer in the series kills their victims as horribly as he does. He skinned multiple people alive in the army, skinned two more people in search of Freebo, skinned a 14 year old boy to death for helping the police with the investigation, tried to turn one of his workers into a scapegoat, nearly killed another character in a much longer and slower skinning process, and is revealed to have been doing all of this simply out of narcisism and sadism. His goals were to defend his "honor" and "reputation" and more importantly (for him), to relive the experience of torturing people.
Moral Event Horizon?
He crossed it by slowly torturing a 14 year old boy to death by skinning him alive just to serve as a message to anyone else who was willing to help the police with the investigation.
As the killer with the most heinous method of disposing of their victims (which is saying a lot considering the large number of killers in the show), I say he should be a solid keep.