i dont think sephiroths meteor should count because it was only through the black materia that he was able to summon it. sephiroths powerful without the meteor though. but i still dont think the meteor should count as sephiroths power. technically necron isnt a villain but i think necrons probly the most powerful FF character. mainly because he has just about as much power as any other FF main villain + he cant really be destroyed and it pretty much says at the end of the battle that he is invincible and he also can destroy everything. and usually things with necro in it E.G. necromancer or necron mean death or something like death. so necron pretty much means the end of all things. for villains though id have to say neo X-death, kuja or kefka. neo X-death is just like necron except he is killed and destroyed. you see kuja use more power than you see nearly any FF enemy use. he destroys a whole planet. i think terra was a small planet and he may not be powerful enough to destroy the whole of gaia but hes still incredibly powerful. and ive not completed FF6 but from what i know, kefka evelvates his power to god-like power and im assuming we never see the full extent of his power. i guess kefka or neo X-death are the most powerful.