Yea, I even survived Omega's Terra Break attack, like always. (Ok, I am boosted like a god in this game 9999hp, 255str/vit/mag/spr/spd/luck, 40%eva, hit/fav/cha. Auto-Pro/She/Has + Ribbon aka 100% St resist, and that's before magic junction, 90%all element absorb.)

Use any of the following:
Squall/Rinoa/Irvine/Quistis
You'll have far greater chances of surviving and dealing much more damage to Omega.

Squall - Renzokuken/Lionheart
Rinoa - Invinsible Moon/Wishing Star/Meteor Shower
Irvine - Fast Shot''255str''/best ammo you can find
Quistis - Mighty Guard 'if you don't have any Autos''/ Shockwave Pulsar 'Go Griever!'