And yet Pica, with just FBH survived Zoros second strongest attack.
And it doesn't matter that Zoro was "banged up". Oda always has finishing blows come when characters are all busted up at the end of the fights. It doesn't factor into anything, because it's a trope. The more desperate the situation becomes, the stronger the character gets.
Luffy was at .01 hp when he launched Bajrang Gun (literally coming back from being dead) and still broke through Kaido's ultimate attack and sent him barreling through miles of bedrock. If his health played a factor into the level of his attack, then a 100 percent healthy Luffy could destroy the entire Country of Wano 1000 times over with Bajrang gun.