Bajrang Gun is basically a nuke in the form of a punch. Just because it’s not a sharp concentrated attack doesn’t mean it’s not lethal. The surface area alone is hard to avoid. Kaido in dragon form is that big, and how fast Luffy zipped Kaido down bedrock is another factor.
Kaido literally said himself that he will take the attack head on which means he could have chosen not to.
As fast as he zipped Doffy with KKG? Remember how much that was hyped and what it ended up like?
The same will happen with Bajrang Gun.