Throughout One Piece's 1000+ chapters, Luffy has faced numerous opponents with a wide variety of fighting styles and abilities. Some he's defeated without much trouble, while others posed more of a threat. One fight that is still talked about today among fans is his fight against Charlotte Katakuri, one of Big Mom's many children.
Katakuri was one of Luffy's stronger opponents and one that could match him literally blow for blow thanks to his Mochi Mochi no Mi powers, which allowed him to copy Luffy's attacks like his Elephant Gun. Despite the Mochi Mochi no Mi's status as a Paramecia-type Devil Fruit, Katakuri could morph his body into mochi as though it were a Logia-type ability. So how did Luffy beat such a formidable foe?
The Time and Place
Luffy and Katakuri had a few scuffles during the wedding ceremony between Pudding and Sanji and the subsequent escape, but their major fight would start on the deck of the Thousand Sunny in Chapter 878 (Episode 850 in the anime) after Pedro sacrificed himself. Katakuri had infiltrated the ship using Brûlée's ability to travel through mirrors and was waiting for their return.
When the group was preparing for their aerial escape, Katakuri attempted to stop them, but Luffy was able to drag him into the Mirro-World so that his friends could complete their preparations and escape. Once separated, Luffy shattered the mirror so that Katakuri and his men couldn't return to the Thousand Sunny. It would be here that the two would go head to head in their first major fight against each other.
The Victory
The two traded blows with Katakuri having the upper hand for most of the fight, mostly due to having his Devil Fruit powers awakened. Luffy was struggling to hold his own, even having to withdraw in order for his Haki to recharge. After several rounds and some interference from Charlotte Flampe, the two finally stood on equal footing as Luffy learned how to predict movements with the Color of Observation Haki and Katakuri injuring himself in the same way he had injured Luffy after Flampe shot him with a needle. They unleashed their Supreme King Haki and once again began trading blows with one another. In the end, Luffy was the last one standing as Katakuri had collapsed.
Luffy's victory appears to be a result of a combination of factors. The first could be that because Katakuri's snack time was interrupted, he wasn't able to replenish his strength. He stated in one panel that sugar was the root of his strength. As he was already late for his snack time and he couldn't finish, he may not have been able to recharge to his full strength if we take this statement literally. There's also the fact that he stabbed himself in the abdomen to make up for Flampe's interference, a grave injury.
Having to fight with an injury like that would most likely have an effect on him, especially if he doesn't get injured so severely often. Luffy is constantly getting injured and has learned to fight through the pain while Katakuri used his Observation Haki to predict and dodge attacks with his mochi powers. There's also the factor of just pure exhaustion. Alternatively, it could have been sheer luck and plot armor that allowed Luffy to win.
The Future
Will Luffy and Katakuri ever face off again? If so, what would happen? It's probable that another fight between stretchy-men could occur for the simple fact that Katakuri would want a fair fight against Luffy where none of his siblings interfere despite Luffy saying there's no such thing as fighting dirty between pirates.
Luffy's abilities and powers have grown since their initial row, and going up against him again would be a challenge to see how far he's actually come. Katakuri too would probably have trained hard for a rematch. The two share a mutual respect for each other, and a fair fight would be a fitting end. However, with Luffy once again facing off against Kaido and the World Government heading to Wano, it's also extremely likely that Oda will focus more on steering towards the series finale than toward a rematch, at least in the near future.
