My God, this is really stupid. That Borsalino has a named technique for creating a sword (Ame no Murakamo), and that said sword is named after one of Japan's 3 Imperial Regalia (along with Borsalino's 2 other signature techniques), shows just how special his swordsmanship is to him.
One of Borsalino's signature techniques is to create a legendary and sacred sword.
Anyway, I've covered the reasons that Borsalino will be Zoro's opponent in
another thread.
Issho has much worse feats than Sakazuki.
When did Sabo outperform Marco vs an Emperor?
Do you mean an Emperor's Commander? Burgess does not appear particularly strong. Lafitte was talking down to him.
That's frankly irrelevant.
Linlin gets clowned on by fodder like Nami, Chopper, Brook and Robin.
Kaido oneshots YC 1 characters like Post WCI Luffy without using his Devil Fruit.
Zoro already used COC when he cut Kaido. It's not particularly complicated.