I don't know where people are getting the idea that Kefka was an ordinary human before getting power from the statues =/

Kefka was given magic in Cid's early experiments. Remember his wholesale slaughter of Espers at Thasma? Yeah, that was before he got to the floating continent. He massacred waves of espers and then killed the empire's best general all without breaking a sweat. Without the statues. I'd call that a pretty damn powerful guy.