Kefka.
That could be an opinion but I'd have to say Sephiroth. It is an opinion and it's usually between Sephiroth and Kefka. Personally, I say Kefka because while was sane and compassionate until he became Jenova's puppet, Kefka was working of his own free, deranged will. Kefka just likes destroying things, Jenova/Sephiroth wants to kill off humans.
probably sephiroth.
Try it in dissidia.
If you play Dissidia, the two can fight. Both can defeat each other.
Sephiroth's father is Hojo, a famous scientist who is in Final Fantasy 7 and Final Fantasy 7 Crisis Core, and his mother is Lucrecia Crescent, who worked with him on the Jenova project.
Doesn't this describe Kefka, Sephiroth, Kuja, Edea
No, they are from different games and have nothing to do with each other.
Kefka Palazzo was created in 1994.
No... Only Chuck Norris can defeat Kefka
Maybe, this can be tested in FF Dissidia but i am certain kefka would win.
No, Jenova is an alien from outerspace. Kefka and Ultimecia are both wizard/witch.