FFXII for me too, though it depends on the criteria. Sephiroth was pretty awesome when I was 10, but his story reeks of too much lost potential (which is true for almost all of discs 2 and 3). Sephiroth still probably wins "most badass," Kefka wins "most battrout crazy," but FFXII's Judges win most well-rounded and engaging -- and are the sort of villains I'd most like to see more of.