HP

MP

EXP Gained

AP Gained

Gil Gained

Steal

Spoils

Morph

Location

15000

400

35000

3500

50000

Ultima Weapon

Cosmo Area

Attacks

Gravity Ball
Ultima Beam
Shadow Flare

Stratagy:

For a Weapon, Ultima doesn't have a lot of HP. Since you have to fight him six or seven times that sort of makes up for it. When he's floating above Cosmo Canyon, it's the final battle.
Make sure you attack with a party that can hit from long range. Use the Long Range materia you picked up waaaay back in the Mythril Mines on Cloud and use Vincent, Barret, Yuffie, or Red XIII with one of his long range weapons. If you're at a high enough level, you can just use physical attacks. If you're not feeling that confident, use any party you wish and have at him with your best summons and magic. Try using Ultima or Contain. Be aware that Shadow Flare is his final attack. Luckily, it only hits one character. No chance that he'll kill everybody at the end, but it can be devastating. So before the final blow is struck, make sure everybody is full on HP and has an Enemy Skill equipped. Somebody will learn Shadow Flare. If they don't die first. Ultima Weapons defeat will open a footpath to the Ancient Forest.