I apologize if this idea has been stated before, but anyway...
Perhaps there can be a certain meter (or something similar) that makes your character become disgusted at all the hacking and slashing they are doing. It is not realistic if people kill a bunch of others and do not feel even remotely regretful (unless they are incredibly sadistic). As people gain experience in combat, they would, of course, get more used to killing, but most would rather not kill for trivial reasons. Of course, there may be a few bloodthirsty races that could be exempted from this idea, but assuming that most other races are not, they probably would rather not kill if they could help it.
Why do characters kill monsters ingame? To gain experience, money, and items. Those things could be gained in methods other than killing. Also, when you destroy a monster, the resulting corpse could smell so disgusting as to make your character retch. Looking on the realistic side, most people would rather not kill if they could help it, and gain exp./money/items in other ways. In other games, the only way to gain those things is to kill monsters.
The main point I am trying to get across is that characters could probably feel extremely disgusted at all the killing they were doing at first, and get used to it later. If such an idea were to be implemented, then people would be forced to use methods other than pure combat to gain money, experience, and items.
What do you think of this idea? Is it horrible, or somewhat feasible?