NPD is fairly uncommon, and people with it are generally completely immune to feedback. You could tell them they have harmed you in X way, and they will simply

NPD is fairly uncommon, and people with it are generally completely immune to feedback. You could tell them they have harmed you in X way, and they will simply be unable to internalize it. 'Immune to negative feedback' is a good proxy. Where as people merely high in the narcissitic trait are more likely to behave that way, they would also eventually be able to understand that they harmed you. A narcissist would be very reluctant to go to therapy. Someone with NPD would believe at their inner most core that therapy is incompatible with their being.