It may be a productive and interesting thought experiment to list the conditions in which you would be willing to kill someone. We might be able to find out a little about ourselves, in so doing.
I'll start:
The clearest situations I would likely exhibit hesitation in killing a person would be when protecting my family and myself. That is my primary loyalty. It wouldn't have to be an action requiring emotional impetus to bring me to do it. No matter how I felt about the situation, danger of this kind is both sensible and obvious to me that I would willingly kill someone. What about a hostage situation where it were to make threats of my family, but certainty of their death still hangs in a balance? That might be harder for me to navigate. It would always be in the back of my mind that regardless of my compliance the danger may still kill them. If I was completely certain that the outcome would result in the loved one(s) death, then I wouldn't comply. I would say sorry to them and immediately set out to eliminate or punish the offender. This situation is as simple as that, in my mind.
I know I am not motivated by greed or lust to the degree where it would ever lead me to kill. That seems drastic and deranged. I am not sadistic enough to do it for amusement or curiousity. Beyond the reasons I have already given, I don't think I'd kill ever.
What about you?