Heya all. First time poster here, so bear with me. This discussion, while intriguing, seems to largely ignore a salient fact: In most fantasy settings, there are *objectively* Good and Evil entities. It occurs to me that to place the person in OP's scenario in a matrix from good to evil, high to low, one needs to place that person with regards to the most Evil and the most Good.
Incidentally, i disagree that Death is the most Evil, since He comes for all (mortal) creatures. He is, at worst, Neutral.
Once located in this matrix, we need to find out if his actions move him one way or another and I am not sure that RL ethics are super applicable.
For example: If OP's protagonist kills merely to stay alive (Curse scenario), it is probably CG at best, CE at worst.
If OP's protagonist is a LG Paladin keeping himself alive by killing thralls thrown at him, regardless of their willingness or alignment, it is probably an intrinsically GOOD act, since he is a Paladin and makes the world OBJECTIVELY better merely by existing. Would he eventually fall? Probably.
Not sure the examples fully or accurately illustrates my meaning but the crux is the fact of objective morality in the game. In fact, it isn't even really morality, since it is fixed and objective but I trust you follow.