People are born this way in the Harry Potter universe and nobody ever changes.
With the caveat that anybody ‘good’ who is doing evil is just under such horrible circumstances! (pearl clutching shrieking) They aren’t bad, they just have horrible backstories. Poor snapeypoo was being bullied for half muggleness, and the girl he loved was so mean to him!
I like those versions though, because they’ve given us some real bangers. There’s one I was reading where the angel who was supposed to hit the soon-to-be hero with a truck starts getting truck-blocked by a character from the fantasy world because he’s tired of the no-effort heroes coming through and beating the crap out of him because he’s the worf.