Second strongest form without any advanced haki and bumzaru assumed gear 4 without any advanced haki defeated Kaido Lmao
And to escape the pressure of that, he had to move far away and take a big boost in order to kick Luffy and do 0 damage to him
Also bumzaru didn't fight gear 5, he was just a punching bag that Luffy could have killed in all the times he caught him in his hands