Quote Originally Posted by The Crystal View Post
Ultimecia can look into Sin or Yu Yevon's mind, see what he think is the strongest thing in existence, rip it out, give it physical form, control it, and merge its power with hers. She wins IMO.


First off, X gives the impression that Yu-Yevon doesn't have enough of a mind to look into. I doubt she could find anything of use. At best, she might be able to create another Sin. I still doubt her power would make much of a difference and even if she did destroy Sin, Yu-Yevon would just take over the Sin she created (it would technically count as an Aeon) and then it would devolve into a battle of wills but I personally feel Ultimacia would fall to Yu-Yevon's madness.

And forget Meteor. Sephiroth have controll over the majority of the Lifestream in Gaia. He can transform an entire planet in his vessel. With a power like that, I think he have a good chance.
Sephiroth never pulled this off and I doubt it's a power unique to him (Aerith showed something similiar to this concept of exerting their will over the planet) so Sephiroth would have to contend with the minds of every lifeform that makes up the Lifestream. Even if he got control, what could he do? Him using the power of the planet to destroy Sin would probably destroy the planet as well which means he would destroy himself as well. The battle is a stalemate.