Depending on the level - befriend them, get them to respect you, then selectively oppose them in a gradual way in things where your opinion only slightly differs from them. Instead of pointing out the lack of empathy, make them actively practice it by asking them repeatedly how a person would feel hypothetically in a situation.
From what I recall, narcissists got their 'narcissistic wound' at a young age, getting them stuck in the emotional development stage where they are in fact the center of the universe. Approval for things they actually do well, as well as balanced disagreement and sound boarding tends to give them what they missed out on and allows them to complete the other stages. As their primary drive is self-preservation, it takes time and effort to overcome such a root fear of not being preoccupied with oneself and protecting their ego.
Once they feel that you are in fact important to them and respectful of them no matter what happens (and that is the hard part as they are incapable of returning that favour for now), you can openly and candidly start disagreeing with them in order to make them take on board different perspectives while still feeling safe and secure in the love and respect they get from you. Building the muscle of empathy while introducing novel ideas will allow them to build the 'muscle' and self confidence to let go of the fear that is holding them back.
Of course...all this is only possible if the narcissist is in fact looking to bond with someone *and* wants to learn more about the outside world. Those ensconced within themselves are probably the biggest long shots and the riskiest investments. And then there is the fact that for most people, this just aint worth doing. You cannot blame them for that. In fact, it can be downright dangerous to your own self-esteem and mental health to do this for a long time. Even shrinks shy away from patients such as this.
So yeah, navigating around them and removing them from your life works
Meanwhile, attacking the narcissistic wound/ego only makes them worse as it confirms their worst fears, though it might help in deterring them from interacting with you. It doesn't help them though.