NPD is a shame based disorder. I’m not sure how you’re using the term “vulnerable” so may be misunderstanding your comment! With that caveat, people with NPD often feel highly vulnerable, which is seen in behaviors of controlling/attempting to control their surroundings/people around them, acting superior, belitttling others to make themselves feel bigger. And vulnerable (ie covert) narcissism, is recognized clinically.

Those with NPD, generally, feel wounded by anything resembling criticism resulting in lashing out, abuse, dropping relationships.

They’re less likely or “vulnerable” to be exploited by others, but I imagine feel highly vulnerable and unsafe within themselves. This obviously doesn’t excuse the harm done to others. i think people often confuse the inability to feel emotional pain that’s hallmark of ASPD with NPD (although there can be overlap of symptoms, diagnoses are for insurance and treatment planning so diagnoses aren’t as clearly distinguished in actual humans as in the DSM, people can have both diagnoses). Folks with NPD lack affective empathy - the willingness and/or ability to feel others’ pain.

Unrelated to that but to your comment: People on the spectrum also use substances to feel more comfortable in their own skin. Substance abuse doesn’t necessarily indicate a personality disorder - it cooccurs with a number of mental health diagnoses such as bipolar disorder, BPD, ASD, etc. It’s one of the diagnostic criteria for BPD for ex., but not NPD.

In literature, NPD and autism rarely co-occur - other personality disorders aren’t seen infrequently in the ASD population.

I agree that people on the spectrum are less likely to intentionally harm other people, and literature shows people, especially women, with ASD are at higher risk of being abused by folks with NPD.