What, no love for Sauron? I thought there were nerdy LotR fans here. How about Voldemort? I bet Harry Potter's more your style, eh? The Crimson King from Stephen King's Dark Tower series perhaps? Although Marten/Randal Flagg/etc would probably be the cooler choice.
If he had the time, the winner'd be Dr. Doom. He's the Batman of the villainous world, after all.