Wow, you really are a fucking brainlet, aren't you? some points, dipshit:
1: Gon only "won by willpower" because the fight he was in had special rules attached to it so that Hanzo couldn't just kill him even if he wanted to. it wasn't some "my will gives me superpowers" shit, Gon absolutely lost the fight physically.
2: Hanzo still could have made Gon give up, but to do so he'd have had to gone to very extreme lengths to the point of permanently maiming him, and he didn't want to, didn't need to(he knew he had several far easier methods to win other matches), and was also not sure if Hisoka would outright kill him if he did ruin Gon like that.
3: As Hanzo himself said, it wasn't simply a matter of Gon being super stubborn, it was the fact Gon somehow had no animosity towards him despite all the pain he put him through. To a trained killer like Hanzo, it was very strange and offputting feeling.
Basically Gon only "won" in name alone. If it was a real fight, he was dead. If Hanzo was just a giant asshole and didn't give a fuck, he'd have lost and been crippled for life.