You mean Zodiark right? He isn't that hard, more than the factor of having a good equipment setup to avoid it's 50% Instant Death Darkja attack.
well i remember that i used the setup to avoid the 50% instant death from darkja and i still get killed everytime. i fought with that fish like 20 times honestly!!. i dont remember if i get to killed him once. but thats good, i like freaking hard RPGs, easy RPGs are a little bit boring jejeje.and i like them really longgggggg. that is an epic RPG. jajajaja!!!. but the point is to enjoy the game. not finish it so fast. well thats my opinion jeje.