Who do you think is the strongest FF main villian in history?
Here are the main villians, and the final bosses if so need be.

Garland- Created a time-loop...
Palamecia- Absorbed heaven and hell
Cloud of Darkness- Controls a portion of the void
Zeromus- Ehh...???
Ex-death- Controlls the void
Kefka- Slowly destroyed the world (as in if left unchecked, everything would have died)
Sephiroth- Ehh...?
Ultimecia- Ended up with Time powers
Kuja- Destroyed a whole planet
Sin- Don't forget about that move he does, when he opens his mouth...
Vayne- Yea right
Orphan- Worse than Vayne



I say this...

Ex-death- Come on now, the void?
Ultimeica- Again, Time?
Cloud of darkness- (Parts of the void are better than nothing

I'll finish later...headache...>.>