Is a complete or partial lack of a fear response.
Their amygdala's are roughly 10-20% smaller than average. This means that they literally do not fear the consequences of their actions, on others or themselves. Couple this with an addictive personality (they gravitate toward thrill seeking to better stimulate their dopamine release), and what you get are thrill-seekers with no brakes who have difficulty in either perceiving damage from consequences to themselves or see themselves as not being subject to the consequences of actions to others. Some of this is learned - if you are bailed out every time you make a mistake, you never learn the cost of such mistakes, but the association of fear with paying that cost is just not as high with psychopaths as it is with normatives - in effect, you forget the fear faster.
Psychopathy and narcissism are often co-morbid traits, but they are not quite the same thing. I'm not sure I fully agree with the conventional psychological definition of a narcissist, which tends to involve creating a single dominant outer personality that acts as a mask for the inner personality. Most people assume different roles in different social contexts, and those roles tend to persist over time, though if not exercised regularly they do eventually fade away.
Narcissists have one role. Trump is a narcissist - there are no different manifestations of Trump. He has invested everything he has into Trump as a personality, and there's honestly nothing underneath it, no hidden role of an abandoned child or such similar falderal. I think this is important to understand, because not all narcissists are psychopaths or vice versa.
I've seen Trump as being described as a con man, but I think this gives the impression that he's a chameleon. He's not. Trump makes promises that he has no intention of keeping. He lies. He intimidates, threatens, and blackmails. He stamps his name everywhere because it is his reflection of himself as being the only significant person in the world. In this respect he's not that different from many very powerful people. There is an expectation of adulation, of recognition that you do not matter; if you do not bend your knee, you're gone. That's the only thing he understands, and in many respects it's the only thing he can understand at this point. He's a psychopath because he has no sense of responsibility. To his dying breath, he will hold only anger in his body, because the world does not respect him.
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