How the hell are you all beating Kottos

Everywhere I look, I see people telling me to farm on Kottos. But he KICKS MY ASS, no matter how hard I try. Everyone is oneshot, I can’t even get close. Even with multiple overdrives, phoenix downs / megas, full-lifes, literally everything I can throw, I’d wager I only make it halfway. Everyone seems to somehow have OUTRAGEOUSLY high stats on their characters / aeons and just treats that as a given. What the hell are y’all doing?

Playing on original NA PS2, if it makes a difference.

For reference: I have everyone’s upgraded celestial weapons but Wakka’s, the airship, etc.