Do you know anyone who had emotional and anger issues, but resolved them and changed their personality?

Yes. After that dangerous person became safe to be around it was a different world for the rest of us. But it's not like he became a nice person.
In 1970 he was arrested for insane driving and investigated for beating up children. Reform began with him noticing that times had changed and he needed to be non aggressive, non violent to be liked. A narcissist can be like that.