Omega is a hard nut to crack, and takes around half an hour, if you can, max out all HP and try and get 3xDefend commands, one per character, 100xDeath to Status-Def-J and then get Zell, Quistis/Rinoa and Squall together at lv100, then use Lionheart as many times as possible, use Zell Booya/Punch rush many times, With Rinoa pray for Invincible moon (will come in a dire fix) with Quistis use Mighty Guard but be careful about curative magic then. In a while Omega should settle into a pattern, try and use a Holy War/Hero on at least one character and summon GF Cerberus to cast triple/double everything. You should have got one Hero some where on Disk 2 or 3 not sure where. Try it and pray, it works