An interesting debate. (FFVI and IX spoilers)
Who do you think would win in a straight out fight Kuja, or Kefka?
Kefka's strong points
1. He has the power of the statues, which is all magic in the world and possibly all magic in existence (in the universe of FFVI)
2. He was able to take down 8 espers at once.
3. Kefka could attack you anywhere in the world with "Light of Judgement."
4. If Kefka stands within a range of the three statues, he cannot be harmed because the statues absorb all magic.
Kuja's Strong points
1. Destroys an entire planet.
2. Has the power of many absorbed souls
3. Kills the ENTIRE party in Memoria (The Ultima spell doesn't destroy the Crystal it kills the party sending them to Necron the main part of the Iifa tree but that is a hole different topic)
4. Can Summon Deathguise, and has tons of Silver dragons at his disposal(always a plus)
5. Teleports the party from the Hill Of Dispair. This counts as something to me considering he teleports you out of death.