a Grandiose one
Calling someone a Grandiose is like saying they're a stupid, overconfident, self-important idiot. It's just a rude way to show you're not impressed.
He said he was the best. I said, 'You're a Grandiose N****r.'
She thought she was famous. I called her a Grandiose.
He acted like he ruled the world. I told him, 'You're a Grandiose.'