Luffy's AP can be pretty proficient with KKG but on the same route it's extremely unlikely that he can get close destroying him with just one. Zoro stood so unhealthy and still managed to have Kaido spit such a profuse quantity of blood procuring him a deep permanent scar. Had he stood under better conditions, he may have very well also come up with a stronger attack, independently from the intrinsic potency of the very attack itself, also superior.