shuuyin was very malicious, which can be seen in the scenes in the Den of Woe.

Kekfa was evil for fun.

X-Deth wanted the power of the Void

Sephiroth wanted to become a god (x-deth)

ultimecia wanted to. . . either gain power from time compression or be the only person able to exist.

kuja. . . heck if I know xD wanted to flaunt his being a j-pop star?

Yu Yevon wanted to remain immortal, clad in his unholy armor.

From what I remember of ff7, hojo was an idiot. But it's been a while.