This excerpt is taken from a post I made in your other thread.

Quote Originally Posted by masamune1600
[...]Ramza can learn a secret ability, Ultima, to Guts. Ultima can be learned from Celia and Lede as Assassins, or from Ultima Demons. Unfortunately, this version of Ultima (the weakest) is the only one that Ramza can learn. Altima uses two more powerful versions of Ultima in his two forms during the final sequence.
Ultima is, depending on your point of view, a rather powerful spell. Unfortunately, Ramza can only use Ultima's weakest incarnation. Altima (as Holy Angel) can use a more powerful version of Ultima (the name remains the same). It does more damage and hits over a greater range. As Arch Angel, Altima can use All-Ultima, the most powerful form. This deals even greater damage, and has roughly the same effect area as a high-level summon.