Sephiroth. Not to think about his name is 'feminine'
Kefka was, for me, creepy, crazy clown, but that's not all. His theme music, somewhat reflects his twisted side, and it sometimes chills me.
For Cloud of Darkness, well, 'out of blue sky' may be stupid, but, in the battle, she made me give up at first try, when I didn't know about *SPOILER*freeing Warriors of Darkness*SPOILER END*.