Ultimate Weapons (Locations and Power-up factors)
WARNING: This page contains SPOILERS for Final Fantasy VII.
In this section, I will give the location of each character's Ultimate Weapon and the special power-up factor for the weapons. I don't know the exact mathematical formula for the power-ups, but I do know what affects their damage. If you want to know the exact mathematical formulas, I can direct you to several locations that do have them.
Cloud: Ultima Weapon. You’ll get this when you defeat Ultimate WEAPON for the last time. It does damage based on Cloud’s Current HP compared to his Max HP.
Barret: Missing Score. This is found on the stairs on the way up to fight Hojo. Barret must be in your party at the time or the treasure box that has this in it will not appear. It does damage based on the AP that is on the materia that is on the weapon. So, put mastered materia on Missing Score to do more damage. Preferably mastered materia with high AP, like summons.
Tifa: Premium Heart. First, go to Bone Village after getting the Highwind. Dig for normal treasure on the upper level, to the left of the ladder. You should get the key item 'Key to Sector 5'. Then go to Midgar and work your way to wall market. Go in the item shop and grab Premium Heart from the machine. This weapon does damage based on Tifa's limit break. The higher her limit level and the fuller her limit gauge, the more damage she will do.
Aeris: Princess Guard. This is only found in the Temple of the Ancients (Four O’Clock door in the clock room). It does more damage if other members of your party are knocked out.
Red XIII: Limited Moon. Get this from Bugenhagen in Cosmo Canyon after the Midgar parachute raid. It does damage based on Red's Current MP compared to his Max MP.
Yuffie: Conformer. It is found in the Gelnika. From the entrance, go up. Take a right and head down the stairs. Search the upper-left corner to find it. Damage is calculated using Yuffie's level compared to her target's level. The most important thing to know about the Conformer is that it does full damage when you use it to morph.
Cid: Venus Gospel. Talk to the man that stands by the rocket in rocket town after the rocket huge materia quest (you have to talk to the guy three times before he forks it over). Its damage is based on Cid's current MP compared to his Max MP.
Cait Sith: HP Shout. You must get this during the Midgar Raid on disc two. Go to the 64th floor of the Shinra building and check the top row of lockers. It does damage based on Cait's Current HP compared to his Max HP.
Vincent: Death Penalty. Visit the waterfall/cave directly to the East of Nibelheim with Cloud and Vincent in your group (use the sub or a colored chocobo to get there). Talk to Lucrecia once, then go fight ten battles, then check the cave again. Death Penalty will do more damage as Vincent's kill count goes up. All kills Vincent has made from the time you first got him count, and you do not need to have the Death Penalty equipped to make the kills count. Note, however, that some things will not count towards a kill. For example, deaths resulting from Poison and deaths from count down timers will not count.