Similarly Zoro cut off the Skull Dome's right horn.
As for Sanji, Kaido melted the left horn, in his fire + a little bit of magma form, the one which King made his Walmart version. Obviously that Sanji can't outshine Luffy's main opponent so casually in the middle of their fight, so Oda made it go that way
Thats Oda lowkey telling us that no one can compete with Sanji in that aspect anymore. Even if characters clothes and body parts are almost indestructible compared to the environment, Oda was willing to do it for Zoro and Sanji. That kind of stuff actually have a greater meaning than it seems in OP (if im not mistaken, Luffy destroyed one of Kaido's horns in the latest chapter)
So it confirms the thesis that only true magma can compete with Ifrit Jambe right now, i mean, supposing Akainu will be able to compete, which im sure he will cuz he is one of Luffy's last enemies, if not the last one, but it certainly wont be that simple to compete with it. Theres no room for flames in Akainu's magma, its magma and only magma that can be freely manipulated, but on the other hand, Sanji not only changed the color of his flames, but started creating lightning which seems to be plasma.
Sanji already surpassed the regular flames spectrum. If he ever gets new flames somehow, it will be simply be one of the most destructive powers to ever exist in the OP verse, magma will pale in comparison.
