@ShishioIsBack that was a great feat from Mihawk, but at the same time, S-Hawk's slash, that cut through a mountain, was blocked by Blackbeard with one hakified arm. In order to break through an opponents Haki, as Zoro himself pointed out, you should have superior Haki (that is, if your base attack isn't far superior in the first place, as it's the case with boundman, who overpowered stronger Haki defenses with sheer force). While good swordsmanship usually has high DC, it doesn't have sufficiently high "raw power" and rather works with lethality, hence Blackbeard could block S-Hawk's slash and hence Jozu blocked Mihawk's slash without being moved from his place, while a basic Kong Gun with average armament could catapult the likes of Katakuri, who have "super hard" defense through several pillars.
Thus, obviously, a Bajrang Gun, which basically is an island sized Kong Gun amplified with hardening, barrier, internal destruction and conqueror's Haki, is magnitudes above Mihawk's slash. Even if Mihawk amped his slash with all of the Haki he had, I have a hard time seeing how Mihawk won't get overpowered, since the raw strength of Bajrang Gun was strong enough to overpower Kaido's blazing Bagua and send him miles through the earth's bedrock, while having protection from Mihawk's lethality through a combination of armament and barrier Haki - the same protection that allowed him to endure Blazing Bagua.
If Mihawk would want to survive, taking Bajrang Gun head on would be the least intelligent thing; he would get obliterated.
