Mog - wind dance to heal the party. If hes in the back row he takes 0 physical damage cause he has 255 def. Front row = 1 point of damage. Elem attacks heal him.

Sabin - Genji Glove + Offering = 8 hits for 9999.

Gau - Same setup as Mog. 255 def, back row for 0 or front row for 1 point of damage. Elem attacks heal him. Rage with Tyrannosaur (normal attacks = 5000+ damage and meteor = 5000-7000 to all enemies).

Locke/Terra/Celes - Pld shield, Ultima weapon. Casts 2 spells in 1 round or use a black belt to counter physical attacks for 9999. Usually both since I dont mind spending 100+ mp to annihilate everything in one characters turn.

In the Snes version, my Mog has soloed the entire final battle. (1-2 people per group and kill them all before the battle starts, or while the battle is just starting leaving Mog the only one alive). He blocks most magic attacks. Almost always stays at max health and any physical attacks laughably hit him for 1 point, no matter how strong the attack is.