It’s all about what sort of group you’re playing with. I run a group for some kids at my school and I know they would be heartbroken if I just straight up killed them.
I’ve only had to do this once though. I made it a lesson about caution. The player was being reckless, and they ‘died’. Seeing how distraught he was, I decided after the encounter, that the other players should roll for a perception check, and noticed the character still breathing slightly. It was nice to see the kid perk up immediately afterwards.
“Oh fuck, that must mean something was there before, keep rolling perception checks, whatever it is must be around here somewhere”