Grandiosity is an exaggerated sense of self-importance and superiority that is a core feature of narcissism.
Narcissists believe they’re special individuals, entitled to preferential treatment. They are gods, the rest of us mere mortals. Their inflated egos lead them to believe they deserve special treatment, privileges, and unlimited attention and admiration. They fantasize about unlimited power, prestige, wealth, and beauty. (In their self-important warped minds they deserve no less.)
Their grandiosity makes it impossible for them to take accountability or accept criticism of their behavior or shortcomings. They’re arrogant, superior, and highly competitive; There’s only room for one at the top, and that’s the narcissist. Duh.
Others in their sphere must either acknowledge the narcissist’s brilliance and superiority—or be relegated to the discard pile. Your worth is predicated only on how worthy you make them feel, nothing more. Doesn’t exactly make for a healthy give-and-take relationship, does it?