How about nobody? The top tiers are all very close to each other and there is no unequivocal strongest among them!! Is that such a taboo idea?
What do you mean nobody? At any point in time, someone is nr1 and holds the title of WSC and perhaps other titles as well, if he is a man and swordsman. If not, then just WSC.
Blackbeard has a strong case since he can negate Kaido's DF and reduce his Dragon Scale armor (assuming that's the secret behind his durability). Shanks is a top tier swordsman and clearly if he slices Kaido, Kaido can't stop it with his durability.
Why would you think that Kaido can win against Shanks 51 times out of 100? And why would that make him WSC? Shouldn't he be winning 100 times out of 100 if he was the WSC?
Considering the fact that 2 strongest devil fruits have been stuffed into Blackbeard tells me that he is severely lacking in other areas.
The fact that Luffy will fight him without 95% of his rubber arsenal also says that Blackbeard is not something comparable to Kaido.
Can shanks land a clean slash on Kaido before Kaido lands a clean hit on him?
You dont need to win 100 out of 100 to be the strongest, a slip up can end the fight in favor of someone else.
Considering that Shanks isnt WSS nor WSM, how can he win more against WSC when he cant win against other two title holders?