It sort of says a lot when Dexter, a sociopathic serial killer, is not the nastiest person on the show. Surprisingly, that honor goes to John Lithgow, an actor who aside from trying to prevent a bunch of rowdy teenagers from dancing in Footloose doesn't normally play the villain. Apparently he's been saving it up, because the Trinity Killer is pretty terrifying. He commits murders in a cycle of threes, reflecting the deaths of his own family murders. Now, that would probably be bad enough to end up on here; serial murder is generally frowned on in polite society. But it's his treatment of Dexter's own family that really catapults him into the big leagues. It's hard to top killing a man's wife and then leaving his young child in a pool of its mother's blood, thus mirroring Dexter's own childhood trauma.