This question came up on the forums I’ve been active on. I think this question has fascinating implications but may never be answered with any degree of certainty.

Where the point of no return (the point at which a narc cannot be healed) exists on the narcissistic spectrum isn’t a question we will probably ever know. However, I have a couple of theories that ping ponged around inside my head.

1. Level of sadism/paranoia. (these traits were suggested by another forum member)
I think the ratio of ASPD traits to NPD traits would come into play–and most ASPDs are at least somewhat sadistic. I don’t know what the percentage of ASPD traits would have to be (and maybe it would vary in individuals anyway) but obviously a narcissist with a lot of ASPD is going to be more sadistic, and therefore more malignant/psychopathic, and that’s the point where no self awareness is possible–when a narc becomes malignant or psychopathic. Paranoia would come into play too, as I think paranoia rises with sadism. The more malignant the narcissist, the more paranoid (and sadistic) they will be.
For more, please see my article about The Dark Triad.

2. Soul-murder/cognitive dissonance.
My second theory about the point of no return is going to sound a little strange. I don’t believe the world is just the physical world we see. I’m not especially religious and don’t interpret biblical events literally but I am Christian (Catholic) and believe with no doubt that evil exists. Whether there’s an actual entity called Satan is not something I can answer. But I think there are evil entities, or energies, and I think M. Scott Peck’s book “People of the Lie” explains all this brilliantly (and was the first book to explain malignant narcissism even though it wasn’t called that in 1983). It was also the book that helped me identify my mother and my ex as MNs.

Anyway, I think it’s possible for a person (a victim of abuse) to be infected with the evil of another person. If it goes on long enough, the victims’ “narcissism fleas” (N traits picked up from their narcissists) can become cancerous and turn into full blown narcissism. If the victim was especially abused or sensitive (or was both scapegoat and golden child) they may be more covert but are still N.
I think choice also has to do with it. If one sides with their abusers all the time, or colludes with them in antisocial acts, I think something in the person’s soul can turn dark.

Once this darkness sets in, a person who was low-mid spectrum moves higher on the spectrum into malignant narcissism and can’t go back to being the way they were. That’s the point of no return. This has happened in wartime, with soldiers forced to do things that go against their morals like killing innocents, or accidentally killing a fellow soldier in combat — when these veterans return they suffer severe PTSD but for some, who were forced to commit deeds that went against their conscience and morals, they crossed a line into evil.

I think the mechanics of what happens is that when one makes a choice or is forced to do something that goes against their morals, there’s so much cognitive dissonance that a split in the mind occurs, where the person, feeling so guilty over their deed that it’s unbearable, takes the side of evil, to correct the dissonance.

I think all PD’s may actually be complex PTSD (c-PTSD) that is more deeply embedded in the personality.

As far as narcisissts lower on the spectrum (low-through mid spectrum)–and I absolutely believe it’s a spectrum disorder like autism–a non-malignant/non ASPD narcissist isn’t evil and hasn’t crossed the point of no return. It won’t be easy to get that “skeleton transplant” (and will be extremely painful!) but it can be done.

I hope my BPD wall of words made sense (someone told me that all BPD’s write posts that are as long as books with a lot of run on sentences, LOL!)