Also as an empath and having been an abusive relationship, it's not great advice to tell an empath to be kind and understanding. It only feeds into the Narcissist's web. However, you can have empathy for narcissists in general because they have also had a life, a childhood filled with abuse to the point where they've developed a personality disorder. It doesn't mean you need to have a relationship with them, and I recommend to stay away from relationships with narcissists, especially if you're an empath. But, yes you can understand and have empathy for them.