He can’t stand being around someone who has high self-esteem and who doesn’t have ego problems, especially if that someone is a woman. Therefore, instead of him working on his own issues and problems, he tries to pull his victims down to his level and destroy their confidence because that is the only way for him to feel valuable and worthy.
Deep down, he is aware of his insecurities and he tries to mask them by diminishing you and making you question your worth because this is the only way for him to feel above you and for him to feel better about himself. Once he accomplishes this, his mission has been successful. So if you really want to hurt a narcissist, you need to prove to him that he has failed to make you miserable.
You need to prove to him that you feel good about yourself and that you see your worth, even though he never saw it. You need to show him that you respect yourself, even though he has never done it. You need to prove to him that you truly love and prioritize yourself, even though he never did because that really is the best possible revenge.