Wow. Who knew anyone actually liked Zeromus, let alone considered him one of FF's best villains. It was always my impression FFIV fans would rather he not exist and Golbez be the real villain.

Also I am happy at all the mentions of Kuja in the lists in this thread.

I think Gabranth was the best character in 12 but while he was an antagonist, he wasn't really a villain IMO. Maybe barely one but not very evil or sinister.

Cid was the best villain in XII as he was FF's best example of a Well-Intentioned Extremist.