Daniel Plainview: There Will Be Blood Not only does he fool small children into thinking they're his child, but he openly mocks them and tells them they're nothing but a pawn to them when they grow up. Plus, he drinks your milkshake.
This guy was great. Not only is he the only henchman that James Bond could never kill, he also sets off metal detectors at airports (queue the big metal smile). "Now, regarding a replacement for [mongolian guy who got put through a grand piano]. Oh, well, if you can get *him*..." - Hugo Drax, Moonraker.
Thinking about it even more, there need to be subcategories for best villains here; Cold-Blooded Professional- Frank in "Once Upon a Time in The West" Ruthless Force of Nature- Anton Chigurh in "No Country for Old Men" Psychopath that Relishes inflicting violence- Alex in "Clockwork Orange" Over-the-top, Ridiculously Insane Psychopath- Kakihara in "Ichi the Killer" Deceitful, Untouchable Monster- Livia in "I, Cladius"