I'm talking about episode 5 specifically.
Fisk does not appear in episode 5 at all. Episode 6 is where they explicitly parallel Matt and Fisk fighting, but in that episode, Matt inflicts considerably less horrific injuries on his opponent, and whilst he does attempt to hang him, he's doing so to a huge serial killer (indeed he would be the worst serial killer in US history if he had 60 confirmed murders) who is in process of murdering a child (and indeed definitely will murder said child if Matt fails to win the fight, given he is irrationally attempting to even during the fight!). Whereas the guy he absolutely mauled was a bank robber who didn't actually do anything except point guns at people, make ultimately idle threats, and then leave with a candy! The only thing Matt is preventing there is this badguy reporting back to his boss and/or fleeing the country back to NI (and even then he presumably just delays those things). He doesn't even seem to hand him in to the cops!