User blog comment:Fliu/Chapter 953: Swords and a Fox/@comment-173.218.81.252-20190823082132

I always assumed that Kaido got that scar on from fighting Whitebeard. Just seems like something he would have been able to do when he was in better shape. Plus when Kaido steps out of that crater from his suicide attempt he talks about Whitebeard doing it right, meaning being able to hurt him.