most powerful FF villain.

[The Crystal]

And in my opinion, Ultimecia is the most powerfull because she can absorb everything(including the other villains).

Except, not. For one, she'd have to survive the full time it takes her to compress time and space without Kuja literally blasting her to atomic fluff. If Squall and gang, who never demonstrate abilities in the KT range, nevermind MT or TT, can do it, Kuja- the planetglasser- could pretty much do it without effort.

And honestly, smeg opinion. SOD and feat analysis is a far better method to determine who is the most powerful, since it's objective, and has to do with what each villian has actually done.

You are right. For some reason, i forgot that Ultimecia need time to be compressed, to be capable of absorbing it. What an idiot i am. And what is SOD?

Feat analysis is not a very good method to determine who is the most powerfull. Because you can give many different interpretations to a single feat. Depending of your interpretation, a character can seems to be more powerfull then what he/she really is, or vice-versa.