I see so many bring up this as an example of Kaido inconsistent powers and so many more finding the weirdest head canon to explain it, yet no one brings up the fact that Kaidos been tanking heavy damage from the strongest rookies up to that point so naturally his attacks aren't as effective as before hence why Law and even Kinemon aren't completely knocked out from the ONE hit swing. Like this was AFTER Zoro did this
And even Kaido said that shit hurt and when he finish taking out the all the rookies. We see him for the first time catching his breath
Proving what Luffy said to be true. That their attacks are taking a toll on him after all. Followed by another extensive fight with Luffy in a CoCk battle where by the end he was seen once again catching his breath showing signs of fatigue, and that even explains how Kin can still
barely remain conscious, before being
put to sleep by Kindos sword taken out by Kaido with just a sword.
Who said he hasn't put him through extreme situations. And besides would it even be anymore extreme if Luffy life at the point wasnt completely on the line like with Katakuri and the BMP. A good explanation for why Kata has his type of haki without sparring with big mom definitely can be him facing countless strong marine forces or sparring with other YC and their force as well as totta land invaders for decades. All the while perfecting his image of being someone untouchable.
You cant call it an asspull when there's a line of logic as to how Luffy was able utilize CoCk Haki while others haven't before. Luffy came to the conclusion
on his own that you can apply CoC with your attacks, and he only understood that by facing a Yonkos attack multiple times at that point. And when Kaido stated that only a few can utilize it, that explains why even strong fighters aren't fully aware of the technique. Makes sense why Doffy and Kata didnt apply this technique because they were already strong without it and most of all,
they never wanted to go up against a yonko in the first place. Even if they did they probably wouldn't be crazy enough to fight against a yonko twice to fully grasp the nature of their attacks like Luffy did with Kaido.