An exaggerated sense of self-importance
Having a high sense of self-importance is very important, as it helps in making life decisions. However, high conceit in its exaggerated form can be very toxic. People with narcissistic disorder feel critical that in the process when they see every other person be less critical, even in situations where they should be humble, slow to speak, and quick to listen, that narcissistic nature in them does not allow them to be.
Take advantage of others to achieve what they desire
People with narcissistic personality disorder think about themselves alone. They care less about other people, and they do not care how to hurt a person is (this person could be their friend or a family member), as long as they get what they want. In their heads, they think they compete with everybody they know, so there is a toxic competitive nature in them, and these make them take advantage of other people to get their desires.