IT IS ZEPHRAM COCHRANE
Escaped from the love embraces of the Companion he seeks his vengeance on Starfleet and earth for leaving him on that shit hole after ALL HE DID for mankind's future.
I realize your being facetious, but that's actually worth giving some serious thought to. Well, for a moment, anyway. Him somehow being the villain would certainly be more mind-blowing than it being Mitchell or even Khan.