Everyone talking about rep reminded me of AO's rep system which I think would work nicely in this game. Basically, you have rep tiers, and the higher rep you have the more rep someone loses for killing you. This works because if someone has a really high rep (meaning they never hurt anyone) you lose a lot more rep for killing them because the chance of them attacking or trying to kill you is very low. Whereas someone who has a lower rep and is more likely to ambush and kill you in a dungeon you lose less rep for killing because they could be a potential threat. I think this system would help deal with the 'I have to kill them before they kill me' problem. Now you can instantly see how likely someone is to stab you in the back and react accordingly. I think it also realistically makes sense, because if you killed an innocent priest or something people would dislike you a lot more than if you killed some seedy thug in ancient times