Donald Trump, the narcissist.

Narcissistic personality disorder (NPD) is a long-term pattern of abnormal behavior characterized by exaggerated feelings of self-importance, an excessive need for admiration, and a lack of understanding of others' feelings.[4][5] People affected by it often spend a lot of time thinking about achieving power or success, or about their appearance. They often take advantage of the people around them. The behavior typically begins by early adulthood, and occurs across a variety of situations.[5]

The cause of narcissistic personality disorder is unknown.[6] It is a personality disorder classified within cluster B by the Diagnostic and Statistical Manual of Mental Disorders.[5] Diagnosis is by a healthcare professional interviewing the person in question.[4] The condition needs to be differentiated from mania and substance use disorder.[5]

Treatments have not been well studied. Therapy is often difficult as people frequently do not consider themselves to have a problem.[4] The personality was first described in 1925 by Robert Waelder while the current name for the condition came into use in 1968.[7] About one percent of people are believed to be affected at some point in their life.[6] It appears to occur more often in males than females and affects young people more than older people.[4][5]

People with narcissistic personality disorder are characterized by their persistent grandiosity, excessive need for admiration, and a disdain and lack of empathy for others.[8][9] These individuals often display arrogance, a sense of superiority, and power-seeking behaviors.[10] Narcissistic personality disorder is different from having a strong sense of self-confidence. This is because people with NPD typically value themselves over others to the extent that they disregard the feelings and wishes of others and expect to be treated as superior regardless of their actual status or achievements.[8][11] In addition, people with NPD may exhibit fragile egos, an inability to tolerate criticism, and a tendency to belittle others in an attempt to validate their own superiority.[11]

According to the DSM-5, individuals with NPD have most or all of the following symptoms, typically without commensurate qualities or accomplishments:[8][11]

Grandiosity with expectations of superior treatment from others
Fixated on fantasies of power, success, intelligence, attractiveness, etc.
Self-perception of being unique, superior and associated with high-status people and institutions
Needing constant admiration from others
Sense of entitlement to special treatment and to obedience from others
Exploitative of others to achieve personal gain
Unwilling to empathize with others' feelings, wishes, or needs
Intensely jealous of others and the belief that others are equally jealous of them
Pompous and arrogant demeanor

https://en.wikipedia.org/wiki/Narcissistic_personality_disorder