My favorite antagonist has to be Johan Liebert from Monster undoubtedly. Johan is a force of nature, he's a near mythical figure shrouded in mystery who's every appearance is a major event in itself. Johan is arguably one of the most heinous and terrifying characters every portrayed in fiction but unlike other villains, he isn't one dimensional. Johan has a very complex psychology and he has an agenda and he is willing to manipulate and kill absolutely anyone to achieve his goals and those he refuses to kill, he chooses to corrupt. If you looked up the word monster in the dictionary, you'd find a picture of Johan Liebert, and never has a word been so capable of accurately describe such a character.