For the ones talking about Ryuma, Ryuma has no connection with Kaido. Kaido's entire story is based around Oden, who is a samurai he think was so strong, there will never be someone like him again, what Oden did is scar Kaido. Yes, he could have killed him, but ultimately didn't do it, with Oda setting up scabbards' failure of even opening his old scar for it to happen in the future.
And Zoro coincidently is the one holding Enma, with Zoro talking about 'slicing the one rumored as the world strongest', never talking about killing anyone. This was even cleared up by Stephen saying Oda always use this term with Zoro to avoid the word "killing", and from simple knowing how One Piece works, it's logical
So overall then, as stated before, all the connections Zoro has with enma blade, his connections with Oden are simply a setup for him to either open Kaido's old scar again or creating a new one. That's what he'd accomplish. But the one who'd actually defeat Kaido is Luffy, no one else