Kefka is probably the most awesome badguy I've ever come across. He starts out only mildly annoying, so I got constantly surprised at how evil he truly was. Or perhaps twisted is a better word, as everything he does makes so much sense from his perspective. The journey he makes from mildly annoying to extremely dangerous and evil is something rarely seen, and his personality adds another layer of awesomeness to his character.
Vivi is a great character as well, definitely the best one in FFIX, but although he holds up well within the medium he can't really compete with the best characters outside of videogames.
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