I dont think Big Moms Heavenly fire would have defeated Luffy if reiju could endure it, But a clean Attack from Kaidos club would've definitely done the job. Thats why I brought Law up...... The point is there's still a massive Gap between the Yonko and the supernova. Kaido could have ended this fight in 1001 if he was serious and didn't let them just throw attacks at him.
I don't care your point if there's big gap or not, it's just bothering me when law save luffy just once and all credit goes to him, put your biased glasses off dude