I've just been fighting with Kitten Sith in my spare time to level him up. I plan on getting him to level 30 (he's at 29 now, so it won't take too long), so he'll have three Dice for his Limit Break. I still don't know if I should use Dice (random, yet somewhat solid damage) or Slots (random, a variety of effects not limited to just damage). I also tested out Bahamut, it does ~2,000 damage! Unfortunately, it costs 100 MP...man, I wish I bought a MP Plus Materia back in Cosmo Canyon...

I almost beat him a couple days ago, but I screwed up and he got to attack twice (sometimes it seems like he cheats or something). I'm sure if I keep trying I'll get him eventually.