I find information conflicting so far. We see the Pirate King getting hyped up to test Oden’s power, and we see him clash with Prime Whitebeard. There is no doubt that he should be on that tier. However, Oda makes it sound as though it was such a huge feat to give Kaido 1 wound. Unless Kaido possesses Majin Boo level regeneration, I don’t see how he would only manage to wound him, and only once at that.