So you wouldn't kill in the defense of your loved ones and every single person on the island? As I said earlier in the thread, part of training someone to carry a weapon to be used to defend themselves, loved ones, or innocents, is to have them come to terms with taking another's life. Also to define the limits when they would use potentially deadly force.
"Normal people" who decide to provide for their defense and that of others, are led to come to terms with the necessary boundaries to do that. Some decide they can't do so. Fair enough. Those who move forward are willing to kill if necessary within the boundaries where they have no choice.
"Normal people" facing an ugly enough threat have killed the threat for thousands of years. As I said earlier, the MC had no choice, what sucks is had they left as soon as they knew of the plague he never would have been in the situation.
Also we (not you but several folks here) have been throwing the term assassination around pretty freely. Assassination applies to killing prominent people heads of governments, major figures etc. Killing the inquisitor is murder, but not an assassination.
Uhhh, I hate to tell you, but just because training someone to use a weapon to kill or maim another human being doesn't make someone come to terms with taking another's life. Training to take another's life and actually being faced with the decision to purposefully take another's life are two very, very different things. I was in the Army and scene combat. I've hunted before, etc. There's no other feeling/emotion/etc. for you have/process when attempting to kill another human. It's a lot different than killing an animal. Granted, not everyone follows this. Some are able to kill someone else without as many issues, but the average person, it's monumental. If you read stories/watched documentaries, this comes up in the Vietnam War. Most American troops, even when trained to kill another person, would shoot above head height because they couldn't bring themselves to shoot at another person. Even if it was war. This can be traced to many wars. Granted, training has evolved to attempt to make it easier for a person to shoot another human, but that visceral fear/feelings/emotion is still there for a majority of people.
Yeah, the MC may not have had a choice, but it's still that visceral response. He just killed a member of the Church, was another human that wasn't a sanctioned duel and had time to prepare himself mentally, etc. And unlike movies, again for the majority of people, just because you kill one person, it doesn't necessarily make it any easier if you have to kill again. Unless you're a sociopath.