Pale-Man (Pan's Labyrinth) - He eats people, and we didn't see if he could be harmed by human means. I go with supernatural over The Bride.
T-1000 - This was the toughest decision on this list. First off, the T-1000 is an unstoppable killing machine. Second, bullets do nothing to him, nor do flamethrowers. Third, Ripley hates robots. Although I wonder what would happen if he touched Alien DNA?
Jack Torrance (The Shinning) - He sees dead people.
Michael Corleone (The Godfather) - Have you seen Godfather?