Can someone explain Donald Trump's EXTREME level of narcissism?

[The Velveteen Ocelot]

3. Malignant narcissism.

This article explains it pretty well: https://www.psychologytoday.com/blog/neurosagacity/201702/malignant-narcissism-collision-two-personality-disorders (scroll down a bit)

"Malignant narcissism is a blend of two disorders that pose problems interpersonally for their victims - narcissistic and antisocial personality disorders. It is not uncommon for others to feel anxious, intimidated by, and fearful of people with this condition. The combination of poor empathy, coupled with aggression, hypersensitivity, and suspiciousness can bring pain to others.

Those who interact with malignant narcissists often consider them jealous, petty, thin-skinned, punitive, hateful, cunning, and angry. Given their shallowness, they are not regulated emotionally and have beliefs that swing from one extreme to the next.

Their decisions can hurt others because they rank relationships and people based on superficial standards and categories. They want to land on top, even when pretending to be altruistic or engaging in an activity that should not be 'all about them.' They often view the world through a primitive binary lens (e.g., winner/loser; smart/dumb; rich/poor; pretty/ ugly; black/white) - all the while sustaining the belief they are superior. This is likely associated with problems processing emotional information, which reflects faulty neurobiology."

How he got to be that way is not clear, however.