I enjoyed 8MM, but each villain goes down anticlimatically.
I think I'll also mention Pennywise in the It movie. Like Candyman, a five star performance in a two star film.
Jack Nicholson in the Shining was a hell of a performance. I suppose he straddles the line of monster and regular guy, as he was, you know, possesed and all.
As far as regular guys go, I'm a Leatherface fan too, but I'll always say Patrick Bateman. I love that bastard.