
I've acquired Dissidia. And I'm seriously amused here. Because, of course the first Chaos character I unlocked was Sephiroth, and then killed Cloud a few times just because, and then acquired his alternate outfit. For most of the other characters, this is either a different coloured version of their usual outfit, or a different set of clothes they've worn. For example, Cloud has his basic SOLDIER uniform on, and his alternate costume is his Advent Children getup. (Not KH, unfortunately. Or a dress.) Sephiroth's other outfit? He loses the coat.
Admittedly, that is the only other 'outfit' he's ever canonically worn, and he gets the wing as part of his special move, so that doesn't count. But still...
Also I'm developing a weird fondness for the Emperor (FFII) based solely on his resemblance to Jareth the Goblin King. And then there are the limitless possibilities produced by collecting up the craziest most powerful characters from the first ten Final Fantasy games and sticking them in a room. I wonder if Kuja could be convinced to call Sephiroth nii-san? Even if only to freak out Cloud...