BlackStar_BH
In Wuxia novels, Martial Artists fight using internal energy (Qi). In this case, when compared to cultivators, martial artists were generally only at the Qi Condensation stage. Peak martial artists (often called transcendents) were at most only equivalent to Foundation Establishment stage cultivators. So forget about the Gold Core or Nascent Soul, because that will never be in the Wuxia story. The peak power of the One Piece Realm, in my opinion is only the Sky Profound Realm. Pirates generally fight in a barbaric way. They had no cultivation methods or martial techniques. The moves displayed were simply the result of continuous battles that were roughly developed. So how could Kaido be on par with a BPS cultivator who had a lifespan of thousands of years?