I changed my mind . . .

[Masamune·1600]

Just so you guys know, there is only one Enemy Skill that is not available at the end of the game. Trine is used exclusively by Materia Keeper, Stilvas, and Godo. All others, however, can still be obtained.

If you wait until the end of the game before fighting Godo, when you have all the E.Skill materia, you can still learn Trine from him.
The Stilva is the only monster in the game that uses Magic Breath.

It's true that one can wait until the second disc to fight Godo, but if one does not wait until Disc 2, the player forfeits the opportunity to add Trine to all four E. Skill materia. This is the only Enemy Skill that's possible to permanently miss, whether applied to one or all four materia.

Stilva is not the only enemy in the game with Magic Breath. The Parasite, also the source of L5 Death, also has Magic Breath. Parasites, needless to say, are located at the Northern Crater, and are thus accessible for the rest of the game.