This was an interesting way to end the fight, because I got the strong sense that Katakuri physically had plenty left in him to keep fighting- in the same way that Luffy always goes beyond his limits. He suffered much less punishment than Luffy, exerted himself less, was fresher for the fight, and I’m sure Luffy hits hard but I’m even more sure that Katakuri is one tough bastard. So, why didn’t he push himself as hard as Luffy did? Why did he let his body quit on him?
Usually the victory condition for Luffy is “win the fistfight”. Want to win more than Lucci or Crocodile or whoever, and use your cardio to punch them some more. That’s a bit reductive I know, but the message of this fight retroactively applies to every fight before. Because this wasn’t the case here. Katakuri could have killed him easily at the very end, but he didn’t want to anymore- because Luffy removed his will to fight. The same willpower that pushes Luffy so far beyond his limits every single time, the conviction, the fighting spirit, the drive to protect the people he cares about, the rock solid confidence in the reason he’s fighting at all, simply through his actions and his behavior over the course of the fight he inspired Katakuri to rethink all of that for himself.
He didn’t want to protect his Mom anymore, he doesn’t care about the organization anymore, he doesn’t need to fight to protect his reputation anymore, and he knows he doesn’t need to worry about Luffy being cruel to the rest of his family. He realized that he didn’t need to win this fight, Luffy showed him that without saying a word to that effect. This is what Mihawk was talking about, his magnetism, his ability to affect others and inspire them just by being himself just directly won him the battle of his life.
This is probably going to go down as the definitive Luffy fight for that reason. Something that gets misunderstood in a lot of bad action is that a fight should just be a fight for fighting’s sake, but one of the consistently great things about One Piece is that the fights represent so much more than they are on the surface. This fight represented Luffy breaking a troubled soul down to the foundation and building him back up by example into a better, more complete human. He didn’t dominate him, he didn’t violently exert his supremacy over him- he showed him the way. It’s surprisingly wholesome considering he showed him how to accept himself by beating the shit out of him. Luffy’s win condition here was to get through to Katakuri and change his entire outlook on life for the better, such that he doesn’t feel the need to continue fighting. It’s like peace through force. If there’s a more Luffy way to win I don’t know what it is.
*Theory by Gravelord-_Nito