I always find Bastards to be like-able characters, but half the time bastards are protagonists , not villains (ie, House, Gene Hunt, Jeremy Clarkson
, Blackadder), however, one guy comes into mind when I think of Bastard Villains, Ben from Lost.
He started off as a good character, because he was a cocky bastard at the start of season three, but he's even better now, purely because he's a Psychopath by the end of the third season.
I suppose Q of Star Trek although he's not really a Villain, he's just a bloke with Godly powers who like to piss of Picard.
Darth Vader and the Emperor are also fantastic villains.