Ok, I'm going to put this is a realistic scenario, I know that the game itself has its realistic and non-realistic portions to it. You, a man who just has lost everything due to the apacolypse (Zombie apacolypse) are alone, raiding a store for food, water, guns, whatever it may be. You finally find a gun and you come across a man, one that you don't know at all. He also has a gun, now what would you do? This complete stranger who has the ability to kill you swiftly that you actually WANT to team up with? I wouldn't trust him. Another scenario you have actually "befriended" somebody, you both have excellent weapons and good supplies. You get into a fight and suddenly the bonds between you break and it is unnoticed at first, but then you guys become detached from each other. He may/may not have a bit of mental trouble but if the trust of one was lost, what would you do? Would you constantly worry yourself to death thinking he is going to kill you? No, I'd kill them straight away. These scenarios I have thought up explain, 1. KOSing, Killing on Sight. Scenario 1 explains that you meet a complete stranger and you are expected to actually trust him? No. 2."Mindless" PvPing. None of the scenarios actually explain why but I cannot tell you how many times I have let a new player who has NO weapons live. Later I see them when they have a weapon and they kill me. In Cherno, and Elektro you cannot expect anything less than basically genocide, it'd happed in the real world as well. 3. Lack of Co-Op. Scenario 1 & 2 explains this. Say you don't kill the stranger from #1 and you actually TRUST them. They don't trust you and they plan to kill you later for their own good. You, jumped the gun, you basically trusted somebody that you shouldn't have. That is your fault nobody elses. Trust friends, not possible enemies. 4.Lone Wolves. Your Karma idea may promote Co-Op because of the benefits but it extremely punishes people like me, one who stays alone throughout the map. What do I gain out of this? Nothing, absolutely nothing. 5. Karma, in general. This has been said before but I will say it again, Karma is fictional and not real. As many people actually may believe in it, most people don't. This is adding more unrealistic properties to the game that we actually WANT to be realistic. In a zombie apacolypse I could kill you and nothing bad would happen to me, no consequences at all. I'm completely sorry to say this but I think your idea is a bit farfetched. 6.Bandits. Bandits are people too.