zanmato , possibly

[farplaner]

Maybe I'm crazy, but even if I offer him 200 gil he's done zanmato even against bosses. Quite often. I used to give him a lot of money, but with each playthrough I realize that it really doesn't take that much for him to pull off some nice attacks. Or I'm lucky. I never really go above 1,000 gil. He does just fine without it

So are you playing the PAL version?