This is a theory I put in a corner of my mind a little while ago now, but I started thinking about it more and more since we started Wano. Luffy will not defeat Kaido the usual way (beating the crap out of him with brute force).
Kaido is the captain of the Beast Pirates, a collection of Zoan devil-fruit users (artificial and real fruits). That’s the whole theme of his crew. Kaido is not a regular human, he is the King of the Beasts, the most powerful creature in the world in term of pure strength. A monster that I’m not sure we can call human at this point.
Nothing and no one can injure him. Not swords, or bullets, or falling from from the sky. Not even himself. He truly seems indestructible. And since it seems to be his most defining feature, I would argue that his body is even more invulnerable than Big Mom’s.
How can Luffy hope to injure such a monster? Simply put, he can’t.
Instead, I think that he will use a way more impressive and badass to win the fight: his Conqueror’s Haki. That’s how he put every beast he encountered so far into submission and that’s the most fitting way to defeat the King of the Beasts himself…
Luffy has something that Kaido seems to lack: an incredible will and an amazing fighting spirit. Luffy is will incarnate. It seems only natural and fitting that the final confrontation will not be a clash of strength but a clash of will.
I mean, how can a man that gave up on life and always tries to kill himself can hope to compete with the strength of character of Luffy?
Maybe that’s just me, but I think that Luffy defeating a Youko not with his fists, but his Conqueror’s Haki will make for one the most hype moment of the entire manga. Putting the most powerful beast in the world into submission in front of the entire world would be a feat only the Pirate King can do.
*Theory by a_pinnari