Narcissism has been a hot topic in media over the last few years. It is important to remember considerable subjectivity is involved in judging narcissism and there's always a risk of personal bias in such assessments. Different people will assess grandiosity, hypersensitivity to evaluation, and lack of empathy differently depending on their worldview and the context of the behavior. Furthermore, people sometimes throw out the term without consideration of narcissism as a continuum.
Sensationalism in media gets more clicks but may pull behavior out of context and lead to presumptions of a personality disorder where none exists. Despite these ills of media, media also can teach us that some people who appear rigidly narcissistic turn out to have far more flexibility and interest in growth than people assume when they hit the dislike button. Consider those in media who turn out to be totally different away from the camera or those who surprise you with their ability to take in feedback to change.
When writing characters, it's essential to consider the continuum of narcissism because where a character lies on it has implications for their character arc. Characters with merely narcissistic traits may better lend themselves to a growth character arc. The key to writing a character who grows centers on creating a multi-layered person who demonstrates some interest in others and a willingness to reflect on the implications of choices when confronted. Perhaps your character struggles to take in feedback but later reflects upon it. Or perhaps the character struggles with grandiosity and hypersensitivity but shows empathy for others' reactions when attention is drawn to the problem. For characters with a flat character arc, you have more freedom to portray more extreme narcissism because of the character's lack of growth.