Before you fight, make sure that Squall's 'Strength' is at least +40% or +60%. Use Aura first, then Haste, then Triple. Concentrate on getting Squall's HP low and using his desperation attack to attack the weapon. Combined with Merton, Squall should deal 8000 to 9999 damage by himself! You should finish the weapon in 2 or 3 consecutive rounds. Why these spells? Aura makes it easier for desperate attacks to appear, even with average or high HP. Merton renders the target's 'Defense' power useless. Haste lets you attack more frequently so the weapon can't get an attack off, and Triple lets you cast three spells in a row.

Finding Ultima Weapon and Bahamut

On the southwest corner of the world map there is some hidden ruins that has a place to land the Ragnarok. (This is where Bahamut can be found). The trick to get Bahamut is simple. Once inside the ruins walk the the center where the computer is. (Every step you walk is a random battle). Once there you'll hear Bahamut growl and you'll get two options, so answer the first one. You'll fight a red dragon. After that you'll be given another two options and answer the first one again. The second one will transport you outside the dungeon. You'll fight another dragon and after that you'll be given two more options and a hidden 3rd option. (Note: Sound familiar? The Shinra Mansion letter when finding Vincent in FF7?). Of course answer the third and you will fight Bahamut.

After that you'll not only have the Bahamut GF but a hole will appear in the ground. Now when I did it I could not enter the hole until a long time later in the game. (After I got Laguna to hang out with the party.) I went back to the hole later and saw a huge plant that I used to climb the down the hole. This part is pretty tricky. Ok once your in a computer it will say something about 2 locks, and it will show you a diagram of 20 squares which 16 them are filled. You'll know what I mean when you see it. Now there is a door on the floor that'll open up when the computer is finished. Go down. Now when you get down the floor there is a computer at the bottom of the stairs that will give you three numbers which are 4,2 and 1. Answer 2. You see a display that subtracts 2 from the 16 filled squares on the display and the door to the next floor. Now go down and you'll see another computer at the bottom of the stairs, but IGNORE IT FOR NOW. There is another computer to the left. go to that computer and it will subtract 4 off of the display leaving you with 10 squares left. (The trick is to get the number 10 twice. You'll see how in a second.) Now the door in the center marked "0" will open. Go inside and go to the glowing yellow computer to the right. It'll add seven more squares to the display giving you 17 squares. Now leave the room and go back to the computer that I told you to ignore. It will give you 3 options, 2,1 and 0. Answer 1 and the door will open that'll take you down to the next floor. (Repeat this step for every floor down, and the final room will take 4 Squares away leaving you the 10 again.) Now all you have to do is make your way to the bottom and fight the Ultima weapon. (MAKE SURE YOU SAVE).