Most of them are really good and some of my favorite themes, but I'm giving a shout out to Kefka cause his theme is more unique from the rest which are all trying to do their best to emulate Bach's Toccatta and Fugue in D Minor and Mussorgsky's Night on Bald Mountain. Kefka's theme actually starts off a bit whimsical before finally dropping into a more sinister military march, so it has always stood out to me more than the other villain themes.