Omega is impossible
If you begin the battle with hermes sandels (the only way to get haste for alot of classes) he still gets first attack and opens with Blaster to kill you instantly
If you wear a Wall ring you have to figure out a way to haste because your doomed without it. That leaves just a Time mage and Chemist, neither of which stand much ground against him.
A ninja can get first strike then use the magic lamp for carbuncle, but Fuma shurikens for only 2000 HP dmg woah mann
Then there is his counter attacks Encircle.... nuff said. Missiles and Mustard bombs inflict gravity damage so who cares about how much HP or defense you have!
Also his beam cannon causes lasting drain damage.... if your hit with Mealstrom your HP drains to 0HP before you can do a thing. Effectively, Mealstrom is an instant death attack which can't be defended against with reflect/bonemail/ribbon etc
There are two things i can think of left to try. How much MP does he have, and how many elixers/turns would it take to wait him out? Or try zapping his MP if i can. Otherwise, i know he can have the Stop status inflicted on him which can remove his ability to counter attack. Question is, how do you stop him? The spell Stop failed several times when i cast it. Is there a Mix combo or Blue magic spell or something.
My last hope for victory lies with a Time mage. Haste on self, heal for 20 turns until an opening to attack arises again.... cast Regan to hopefully counter his Beam cannon - Mealstrom combo. And cast Stop before using Bolt rods. Even if that could work i will need 99elixers, to max my level and master all my jobs.