so I faced omega yesterday and beat him my first try and I'd like to share my strategy with everyone. You will not need to defend because you can kill him before he even terra breaks!!!
MAKE SURE YOU HAVE THE BEST MAGIC WITH ALL CHARACTERS AND JUNCTINO 100 OF ALL!!! (except rinoa). You should have ultimas, meltdowns, meteors, triples, auras, full lifes, curagas, hastes...etc
The party is squall, zell, and rinoa
make sure all characters have auto-haste, spd. +whatever the highest is and vit. +60. Zell and Squall should have str. +60 and rinoa should have mag. +60. Give revive and recover to squall and zell. It doesn't matter what attacks rinoa can use...
rinoa should be junctioned to use her meteor limit break with angel wing. I left meltdown on her to...cuz I just felt like it. You can take meltdown off if you want and cast it before she goes into angel wing, therefore she will perform meteor everytime.
alright...so that battle...
instantly cast triple and aura on all characters. you can put rinoa in instant angel wing. now, just beat the hell out of that a-hole omega with squall and zell. The only time you should have to cure is before and after he uses medigo flame which is after meteor. If you are lucky like me, he should be dead right after he uses gravija. Never getting to his ultimate terra break! OH NO! If you have trouble killing him that fast , just equip defend to zell and squall. Giving it to rinoa should be pointless, but in case you have to revive her before a terra break she might need it. Now, after gravija I'd suggest using zell and squalls limit break twice more, then defending until terra is used.
NOTE: your characters should be at lv 100 with 9999 hp for this.
That his how I powned omega yesterday and I hope that some people who have trouble find it helpful.