I’ve seen over 400 dead bodies. But I worked most of a decade in a funeral home in high school and junior college.
No fictional character can kill unless they are particularly well written but the question is what is paramount when a character kills? Realism or metaphor? Metaphorically, when a hero kills, it can be a form of defeat even if realistically a character should kill to achieve some fictional goal.
Across the cultural life of humanity, murder excludes hope, foregiveness and love, so if that is the lesson of the sermon then the hero should kill. But even then, consequences can correct the transgressions.
Walter Kerr wrote that tragedy has happy endings and comedy has compromised conclusions. The tragic heroes often commit murder and then die or otherwise suffer for it returning balance to the world. If heroes kill it should be a tragedy.