I miss my old FF8 board...but they were great at advice:

[Auronhart]

No, I'm talking about the challenge in which you do not junction the whole game so you cannot max your stats. This challenge = no commands except limit break and attack and horrible stats. Plus it isn't a walk in the park even to get to omega. (it isn't too bad though)

Alternatively you can do Squall's Lionheart (or try to) -- 100 000 hp aprprox, Irvine's Speed shot, 90 000 hp one time, or Quistis' Shockwave Pulsar (200 000hp). But hurry the hell up. Your goal is to get Omega Weapon to die before Medigo Flame. All other attacks won't hurt you one bit (usually) because you should have 255 spr.

You probably should change Quistis' damage to 20,000. Plus, how about the Rinoa Angel wing attack. If you just leave meteor in her inventory and do angel wing it will kill omega faster than everyone except possibly Zell guaranteed. (plus it pauses it so you can use somebody else's limit.