Matt is actually a devil and spends his time beating criminals to a pulp on earth, because why not make sinners suffer on two dimensions? Frank still becomes the Punisher and thinks killing is the best plan. Matt only disagrees because killing means his victims can't suffer any more on this plane, but he lies and keeps up his "moral" facade.

This goes on until one night they both track down a Very Bad Person and Frank kills him and Matt just can't hold back his frustration because godDAMMIT HE WAS GONNA BREAK THAT GUY'S LEGS. The truth comes out and Frank feels really conflicted because he does want these bastards to suffer but Matt is doing it for the wrong reasons.

Now that he knows Hell is totally real, does Frank still feel the same motivation to kill? What's the difference between killing them and leaving them to Matt? Is killing now a mercy? And what is going to happen to his soul?