Oda wrote himself into a corner the moment he introduced Kaido as a villain.
The amount of @$$ pulls + plot contrivances that nerfed Kaido is astronomical, off the top of my head I can't think of another arc villain in Shonen that was nerfed as heavily as Kaido.
- Fighting 8 of the 9 Red Scabbards
- Deciding to lift onigamshima
- While the island is lifted fighting the Supernova, knocks out Luffy
- Knocks out Luffy again kicked off the island
- Luffy comes back and gets murdered
- Luffy returns AGAIN this time awakened
- Kaido decides to take an island-tier attack after so many bouts which manages to knock him into a volcano ... (The assumption is that Kaido is knocked out)