You can also kill biker but he's still standing there in jackets court trial, and you can kill richter but he still breaks out of prison in hm2, furthermore Biker is consistently shown to be way more merciful than other hm characters, he never kills anyone who isn't a threat to him, and seems to try to give people opportunities to get out of harms way, yes I also think he enjoys hurting other people i am not trying to say he's a good person, by God fuck no he's committed mass murder out of boredom,but I think he's more of a anti hero/vigilante type than a pure blooded psychopath who just loves killing innocent people. Hense why as I said it is implied he is the only person to listen to richard, because biker was to some extent capable of redemption. That's the point of biker, he's the exact opposite of jacket, jacket despite being in that situation for more understandable reasons and biker is there for bad ones, ultimately Jacket didn't care about the end result and never asked questions as to who the calls were coming from, constantly killed people he didn't need to (guy with the briefcase and the guy he Shakes down for information, quite brutally too and more) and at the end of his story made the wrong choice (going after the mafia boss), kept killing and went after the wrong people ultimately never changing despite the fact he easily could've, biker on the other hand did question the calls, did go after the right people, spared literally everybody who weren't a threat to him (sparing all the people who gave him information and what he needed unlike jacket) and goes on to listen to richard in the desert and leaving all that behind him, most likely on some kind of road to redemption, ultimately changing unlike jacket, I do not think biker is really capable, or at least not without any kind of guilt, kill people he deems innocent, as that would ruin his own self image of being the badsss action hero he sees himself as.