Now, the debate of which Admiral he will face is irrelevant. Admirals represent the pinnacle of Marine’s fighting force and either one of them will present an equal threat. I personally would love for Zoro to face off against Fujitora simply because they are both swordsmen and I would love for them to finish the fight they started in Dressrosa but I wouldn’t be surprised if he also got to fight Kizaru or Green Bull. Additionally, as they represent the pinnacle of Marines it would only be appropriate for them to also have Conqueror’s Coating. After all, Zoro already has it and there has to be someone with it that goes up against him. There is no better choice for it than an Admiral.
While we are on the topic of Conqueror’s Coating, it’s rather interesting how early Zoro learned to utilize it since it’s said only a handful of strongest are capable of doing so yet Zoro isn’t one of them. Why is that? It’s because pinnacle of strength for a swordsman is not Conqueror’s Coating but rather a Black Blade. With only 2 known black blades, both of which belong to two strongest swordsmen, they are rarer than any other ability. Not even Oden was said to be able to turn Enma into a black blade.
Zoro turning Enma into a Black Blade will not only represent him reaching the pinnacle of Swordsmanship but will also signal that he has surpassed Oden as he has done something he couldn’t.
Zoro specializes in Armament Haki and I think that’s what makes a blade black. I believe Armament Haki is the Haki every swordsman harmonizes with. This is the most obvious in the country of Samurai, Wano, where Ryuo is the concept of flow and has multiple levels to it. As the swordsman continuously pours copious amounts of Armament Haki into their blade it will eventually turn black. After all, the primarily visualization used to show Armament Haki usage is black color. So, in his inevitable clash with an Admiral, as their Conqueror’s and Armament Haki clash, Zoro will reach that pinnacle of Swordsmanship, turn his blades black (either 1 or all 3) and triumph over the Admiral in question.
And The Final opponent Zoro will face is of course going to be…
The World’s Strongest Swordsman, Dracule Mihawk
There is some debate online when and where the two will face off but there is no “debate” in my mind. Mihawk is definitely going to be Zoro’s final opponent and when the two of them meet, Zoro will already have achieved the pinnacle of swordsmanship. With his Black Blades, Conqueror’s Coating and ability to cut whatever he wishes to the two of them will finally meet for their duel. Echoing the words Brook said back in Thriller Bark, when the two swordsman of equal skill meet their duel will be swiftly resolved.
I believe this will take place after Luffy has already become The Pirate King (kind of). When Zoro asked Mihawk to train him, he put his own pride and ambition aside for Luffy. He begged Mihawk to train him not to be able to beat him but to be able to help Luffy become The Pirate King. It’s only appropriate that Zoro achieves his own goal after fulfilling Luffy’s. And besides, Mihawk has no reason to fight Zoro as an antagonist in the “Final War”. Zoro and Him are now Pupil and the Master and since 7 Warlords are no more, there is no way Navy forces Mihawk to fight for them.
The fight between the two will not last too long but the display of their overwhelming skills will be front and center. The two of them will clash with Conqueror’s Haki, splitting the sky (and reaching the Heaven) and the fight will be decided in one swift clash. They will recreate their clash from Baratie except this time it is Zoro who will come out victorious. With this, Zoro would not only achieve his goal but also fulfill the promise he made to Kuina.