This is one of the exceptions I mentioned. It's not the rule. The bulk of Superman's portrayal across media for the better part of 75 years is a character that doesn't kill because he believes in the sanctity of life and because he can avoid doing so. He's not the archetype to use to explore the idea of being forced to kill or to explore the morality of killing. He's the inspirational hero and he can't inspire if he's just as weak and flawed as those he's designed to inspire.