Hank Henshaw is pretty much an epic d-bag. His debut during the Reign of the Supermen arc pretty much introduced him as a complete metal bastard. He nukes Coast City for the lulz (in reality because it reminded him of his former life), has a legitimate hatred for Superman, easily WTF pawned the other "replacement" Supes, is nigh impossible to kill, has access and the ability to overide the most advanced tech in the universe ON TOP of his Kryptonian powerset, etc. He's probably not someone who comes to mind right away, but I'd say he deserves an honorable mention.