OMFG i can't believe one of you mentioned sarouman yet nobody mentioned zaron(no i don't know how to spell them) oh come on 8 feet tall covered with cool black armor and a huge sword, just pure evil not an ounce of good and almost but not quite immortal and thats without the ring of power. he would probably turn vader into cocktail weenies
my second choice would be predator those pussies jason and freddie put together ain't got nothing on it