Undertale did exactly that - I'm pretty sure theyre made by the same creator, Toby Fox.
Undertale, among many, many other things, is specifically designed to challenge modern AAA game structure and break away from the norm of video games. Its not just that you can befriend your enemies and you get punished for fighting; each different monster has unique, endearing possibilities for friendship. You jiggle and dance with slimes, there a frost-bird that tells terrible jokes, one monster desperately wants compliments on their hat. Each one is utterly unique.
There are three unique paths. Pacifist means you dont kill anyone. Neutral is the standard "kill when you have to/im used to video games where you kill every monster you encounter". Then there's Genocide.
There is a unique route where players methodically and maliciously clear every region of every living soul.
All this to say - in an age where most games allow you to murder monsters, enemies, or people for rewards, Undertale (and assumedly Deltarune) treats such behavior with humanity and empathy and the correct amount of abject horror that such actions should warrant.
okok yeah that definitely aligns with what i know/remember of undertale, and i do know toby fox made both games
the weird thing for me is that i’m not really familiar with the norms undertale was subverting
all the characters being unique and possible to either fight OR befriend resulting in different consequences seems completely reasonable from my perspective, i never had a reason to expect anything else