Bahahahahahhaha yeah! I think some writers forget that it’s actually not that easy to kill someone IRL - and sometimes they need to put that into stories. Sure, there can be a character who doesn’t have much remorse - but explain why they have no remorse. Were they in the military? Are they a supernatural species who gives zero shits about humans? Like, just come up with a reason.
But also maybe include someone who is struggling with the whole killing thing to make a cool contrast between the morally grey character, to establish they’re actually morally grey and that this isn’t a standard for this world.
Basic world building and character development shouldn’t be too much to ask for.