Did u see the fight's end?
You realize that they have been fighting for hours before that, right?
This is the same man who took a fucking named attack from the Pirate King as a Rookie & walked it off.
A watered down version of it one-shot Law's equal btw.
Kaido is far from a reliable narrator lol. Oden himself tells kaido to get stronger. He didn't just sit around for 20 fucking years.
Sure, Kaidou wasn't the "Strongest" back then and he gained strength.
Doesn't change the fact that he was a Top Tier even back then. By the time he fought Oden, he had almost ~20 years with his fruit and already was a Rocks pirate before that.
And Shanks and Mihawk weren't top tiers 12+ years ago lmao. Shanks had a 1bil bounty ffs.
Bounty at least gives us a general clue to power level, with exceptions of special cases like buggy
Bounty = Achievements.
That was a Rookie Shanks, he had just started out as a Pirate and was gaining fame.
Like Ace f.ex., when he died he just had 500 million - does that mean he's comparable to Who's Who lmao?
Ace squashes bums like Who's Who as a Rookie, let alone as a Division Commander.
Still doesn't change his Powerlevel, Whitebeard isn't going to take note of people on the level of King/Queen fighting. Let alone calling said duels "Legends".