To me, it's going to be Mihawk and then V. Nusjuro.
Mihawk is the World's Strongest Swordsman but he never fought V. Nusjuro.
Zoro is going to surpass the legend of Mihawk by defeating him soon and will become the World's Strongest Swordsman.
However, Zoro's dream is to become the greatest swordsman EVER and surpass the legend of Ryuma.
V. Nusjuro being from Wano (-juro) and being immortal like the other Gorosei could imply that he was responsible for Ryuma's demise.
So, I think that Zoro will become the greatest ever when he defeats V. Nusjuro.
I even think that Kuina died because of something tied with V. Nusjuro and followed a similar fate than Bonney.
Maybe it was through a cursed sword and V. Nusjuro was responsible for it? That my explain why she fell downstairs.
In Hindu mythology, Venus is associated with Diamon while Saturn is associated with Blue Sapphire.
Zoro vs Diamon Venus is his endgoal.
Mihawk is the World's Strongest Swordsman but he never fought V. Nusjuro.
Zoro is going to surpass the legend of Mihawk by defeating him soon and will become the World's Strongest Swordsman.
However, Zoro's dream is to become the greatest swordsman EVER and surpass the legend of Ryuma.
V. Nusjuro being from Wano (-juro) and being immortal like the other Gorosei could imply that he was responsible for Ryuma's demise.
So, I think that Zoro will become the greatest ever when he defeats V. Nusjuro.
I even think that Kuina died because of something tied with V. Nusjuro and followed a similar fate than Bonney.
Maybe it was through a cursed sword and V. Nusjuro was responsible for it? That my explain why she fell downstairs.
In Hindu mythology, Venus is associated with Diamon while Saturn is associated with Blue Sapphire.
Zoro vs Diamon Venus is his endgoal.