The flashback caused massive damage to Kaido's reputation ngl. Oden needed one attack, Dragon Kaido was laying on the ground AND Oden was really about to strike again if it wasn't for the old hag interrupting the battle.
Oh yep, Oden also got trashed a lot for it buuuut... He got blindsided from behind, Kaido hitting the back of his head with an ACoC blow I assume. Kaido wasn't blindsided when he fought Oden.
True, but still not sure about Oden.
He said that Kaido should never come back to Wano again, after his attack.
So he didn‘t even believe he would‘ve killed him + he believed in the prophecy that Kaido could only be beaten 20 years in the future.
Kaido survived DR Xebec without a scratch while literally being a cabin boy. Obviously different situation and Oden actually managed to leave a scar, maybe he would‘ve opened again after a second time and kill maybe not, but as you said it kinda tanked Kaido a bit. But the Rocks FB made him look cooler in someway.
Then there is his bounty situation. Let‘s be honest his crew is dogshit, bar him and King.
He literally sat in an isolated county for 20 years and doing probably nothing, it had to be his strength that gave him the highest bounty to all living pirates at least.
At that time he had the highest known bounty.