The Master from Dr. Who. Especially when Roger Delgado played as him.
Bane was pretty intense. But someone like James Moriarty who's scarily smart and a little psycho is something I feel is good in a villain too.
hannibal lecter by a country mile
Fu Man Chu.
Dr. Smith from "Lost in Space" TOS...
Death, in the movie Bill & Ted.
The Overlord from Spacehunter 3D.
Whoever is getting trashed by Chuck Norris
PEIN from Naruto! My 'All Time Best'.