Kaido's crew is litterally built up of former pirates broken into submission and forced to join his crew, nearly 6 of which were Supernova from the worst generation, imagine who the rest are.. this man has the strongest crew BY FAR, I can't beileve people think otherwise.

Big moms crew is built upon family, so if you're her child you join that doesn't relate much to strength because not every child is going to be a Katakuri, a prodigy, but with Kaido he actively SEEKS prodigies like Katakuri and breaks them into joining, Kid is A PRIME example-

-had Luffy not shown up and broken him outta jail, Kid would've been forced to become a Beast Pirate, no matter how much WILL you have, Kaido knows that he can break you, suggesting he has already broken multiple conquers into joining his crew-

We know Whitebeard values family above power, so he could care less how strong you are, as long as you are his son and Shank's crew is probably built upon the same ideology as Luffy's basically just a bunch of his nakama, I don't think he seeks out pirates for their strength-

-Blackbeard seems to have a similar ideology to kaido, seeking multiple level 6 PIRATES of Impel down basically guarantees a high level of strength but Blackbeard to our knowledge seeks DEVIL FRUITS, more so than breaking pirates into joining him, doesn't really superceed Kaido-

-because Kaido is the only pirate to our knowledge that values strength so much to the point of wanting to break strong willed (NEW WORLD) pirates into joining him and manufacture artificial zoan fruits, the only issue kaido's crew could potentially suffer from is loyalty.