A stiff breeze could have killed Aeris and Sephiroth didn't kill Aeris anyways, it was Jenova. Sephiroth is a frozen corpse inside of the Great Crater. Kefka subjugated the world and lorded over it like a God. "Sephiroth" didn't even manage to get meteor in. Kefka is far superior in all aspects to Sephiroth.