Gilgamesh (Final Fantasy)

Gilgamesh is an optional boss in the Dawn of Souls and succeeding versions of the original Final Fantasy, fought in the Lifespring Grotto.

Strategy
Gilgamesh's Strength stat is huge, and can easily wipe out any party members. His Magical Defense is also through the roof, so do not count on your magic to deal with him. So Protect is your friend here. Also, use Haste if you have it, as it will increase one party member's (preferably your Warrior if you have one) number of hits. Heal when necessary, and repeat the formula until he is defeated. Also cast Invis on your Mages to protect them of Gilgamesh's powerful attacks.