Known to the High Elves as "The Great Betrayer" for his actions that caused the Sundering. Malekith rules the evil kingdom of the Dark Elves of Naggaroth with a cruel iron fist. The stuff I read about the six cities of Naggaroth make me shudder with disgust: Believe me when I say, you don't want to know.
Now, the Witch King is an immensely strong warrior and powerful mage. He's the son of Aenarion, a bit that's not to be overlooked, and he's got the backing of the Dark Elves.
He would be pretty badass if not for the horrible things that I read about his kingdom.