If you play an evil character, it’s gotta stick a little.
And if you’re a character-actor who always gets the evil role. If you play 100 evil guys. Then 100X moreso.
You get into the evil role. See the world through evil eyes and evil motivations.
And over time, It’s gotta bend your personality towards real evilness. Right?
I suppose you could google evil-character-actors. 20 years later, how many got arrested for something heinous.
What do you think?
EDIT
Put more generally : Can habits gained in one context bleed over into another context?
Yes.
Do they?
Possibly. With increasing probability as the habit becomes stronger. And there’s self-awareness to consider. And how much the habit clashes with the new context.
Personally I’d say no.
For what it’s worth I been DMing campaigns for 20+ years playing evil characters and monsters. You have to get pretty elaborate and good at planning “evil” things. I put evil in quotes because it’s acting, you aren’t evil you are playing a role.