I decided I'd help those who are looking for an easier way to beat Omega Weapon. Follow these steps and you'll win.
Recommended Party: The best party of course Squall (NO WAY) Rinoa, Zell
Preconditions:
Must have Cerberus
Should have Doomtrain (but not totally needed)
Must have 9,999 with all characters
Must have 1 Holy War
Must have 3 Aura
Must have Strong Limits
Must be Immune to Death if Multiply of Level 5
Pretty easy so far right? Everything is realtivly easy to get except the Holy War.
Next?
Start the fight.
First cast Doomtrain (for Zero Vitality)
Then Cerberus
Right before its about to use Megido Flame Heal your party to 9,999 now all your party members have 1 Hp which is a good thing
Use Aura on entire party so you get better limits for Squall and Rinoa, More time for Zell
Then use a Holy War
UNLOAD ALL of your Limits (Have Zell use Dual Armageddon Fist [Repetition of Punch Rush and Booya])
Battle over! Works everytime for me!
Oh yeah...
It's attack order
Lv5 death
Meteor/Gravija/Ultima (one of those randomly)
Megido Flame:9998 damage to all
Meteor/Gravija/Ultima (one of those randomly)
Terra Break: multiple hits each doing alot of damage; overall your characters will get 16000+ damge each
Meteor/Gravija/Ultima (one of those randomly)
Light Pillar:9999 damage to one character
Any attack randomly