While I think CoC is part of the equation (as CoC is also will and ambition, including forcing your will and power upon the blade), I think armament is a key aspect, since it is both used to harden and blacken the blade and make the swordsman to "cut everything and nothing, as he wishes", while ACoC mostly works as an amplification of whatever you have, rather than giving new properties.
Mihawk and Ryuma certainly didn't have a black blade simply because they had stronger conqueror's Haki. Zoro even wondered about phrasing it "forging" a black blade, while Road to Laughtale asked, whether Haki alone is enough.
Mihawk and Ryuma certainly didn't have a black blade simply because they had stronger conqueror's Haki. Zoro even wondered about phrasing it "forging" a black blade, while Road to Laughtale asked, whether Haki alone is enough.
If a blade user has to bend a blade to their will to master it. Then completely changing a blade into a black blade is beyond just bending the weapon to the users will. The only power capable of achieving that is CoC/ACoC.
The post from the databook was only talking about CoA haki. The scene showed Zoro adding CoA haki to his swords. Yes, I agree CoA haki alone is not enough to create a black blade. CoC/ACoC is needed.