I a not baby-killing or physical torturer manner:
Sarah Michelles Character in "Cruel Intentions". What she is doing is certainly evil and can not be justified by any means, except a perverted, self-centered mind...
I just noted that there are few startrek villains that are truely evil, but to me, it seems as if Gul Dukat finally was exactly that. He had several possiblities for redemption, and sometimes seemed to work for the good side. But eventually, he was only interested in himself, and didn´t care for anyone else. He never even attempted to avenge the death (murder) of his daughter, he betrayed the Alpha Quadrant to the Dominion in hope of power, he betrayed the Bajoron followers of his Pah-spirit sect, he even tried to betray the Pah-Spirits or at least one of her chosen ones (Kai Winn) when he had the chance to it...
the preacher guy (Caleb?) from the last few episodes of the last season of Buffy....
Hearing the name of Caleb - how was the main "villain" in American Gothic called? (Caleb was his son´s name) He was definitely evil, I remeber the episode where three (or four?) gangsters (brothers?) try to mix up the city, and he kills them all four.
The last of them ends up with manacles with one wrist to a car that is soon to explode, getting a knife (or something like that) to free himself...