Qualifying as the first Disney Death moments in the history of the franchise, Desch goes into the flaming hub of the Tower of Owen to do some maintenance after Medusa goes down, and the party thinks he got burned to death after they were teleported out. By game's end, Doga goes to retrieve allies to disable the curse of the Five Wyrms, and one of his stops is the Tower of Owen - where Desch emerges out of the hub fresh as daisies! His excuse? It took that long to fix the tower.Bad. Ass.
Not as great as Desch, but when you take Unei, the old-woman guardian of the Dreamworld, into the Ancient Ruins, she destroys three boulders of pure Adamanite by striking them with antimatter. Not to mention that she's perfectly capable of running around and adventuring with your party after being asleep for decades.
In the DS version, this includes occasionally blasting your enemies to high heaven with Holy, the ultimate white magic. They don't survive.
Bonus points if you take her to help you deal with Odin. SHE BLASTS ODIN WITH HOLY.
Arguably, Xande deserves a mention as well. 'Rewarded' with mortality? Flood the world with darkness! Two crystals still on the Floating Continent? Send it crashing into the flood! Quartet of kids getting in the way? Send in the monsters! Flood of darkness receded? Guard that fang with a freaking titan! They made it to your tower? Recolour the bosses as common enemies! They're standing in front of your mirror? Curse of the Five Wyrms! Your apprentice rivals bring around the five 'pure lights'? Show them what that old bastard taught you! You still end up defeated? Face Death with Dignity... and send in the Void!