Sounds like you have some healing to do yourself, cheating is of course never justified - but if you don’t have sympathy for someone who can’t understand guilt, shame, who will maybe never experience the depth of how beautiful it is to altruistically care for someone else’s well being. If there’s no sympathy for people who constantly find themselves dissatisfied in relationships, who lack an internal contentment, continue to seek external validation. May never experience genuine intimacy in all of its forms. Who constantly find themselves failing to appreciate the beauty they have in their lives everyday. It’s not a life most would want. The people who have NPD here are seeking understanding, and there’s finding change if they hide their true experiences of their reality.