One trait that seems characteristic of the NPD is his tendency to judge other people in terms of whether they are "strong" or "weak," admiring the strong and believing the strong are entitled to all of the things in life that they can acquire with their strength, while looking down at the weak with pity. This is because the NPD is a creature that identifies with the strong, and that views the weak as pathetic parasites who would seek to drag down the strong and take away the happiness of the strong because the weak are too weak to survive on their own.
When I use the terms "strong" and "weak," I am not simply referring to physical strength. NPDs view the strong as people who are healthy, smart, driven, confident, in their prime, independent, self-sufficient, attractive, and wise. The NPD views the weak as people who are unintelligent, dependent on others, poor, unattractive, or so old or so young that they are unable to care for themselves. The NPD often grafts the traits that he views as weak onto people that he devalues. For example, when an NPD sees a lower income family in a store, the NPD will often assume that they are classless, unintelligent, make poor decisions, and that they are feral, like animals. The NPD is extremely judgmental and his superego almost always provides for him an unyielding judgmental values system that the NPD himself is exempt from but that everyone else must follow.
NPDs essentially associate strong traits with "good" and weak traits with "bad." To the NPD, the girl in high school who is smart, attractive, and charming is fundamentally BETTER than the girl who is overweight, less intelligent, and awkward. These two people to the NPD are not just different, one is objectively BETTER than the other and deserves better treatment, and the NPD balks at the idea that the smart, pretty girl has to sacrifice anything for the unattractive, unintelligent girl. In this sense, NPDs are social Darwinists. But note that the NPD himself is often the less attractive person or less successful person in the room. The NPD remains blissfully unaware of this reality though, because the NPD voice inside of him is telling him that despite his outward failures, his essence puts him in the category with the strong people and not the weak people. The NPD is so utterly convinced of his own special status that he bashes those with the very weaknesses that he himself exhibits while identifying with those stronger than he. He does not do this out of self-loathing; the NPD genuinely believes that he is special and is among the strong and not the weak. The NPD's utter certainty about his own unique status lies at the very core of his psyche and is one of the reasons that Narcissists can never truly change.