自以为了不起
to think and act as if you are very important
Since he got his new job, he's been very full of his own importance. 自从得到新工作以来，他总是自以为了不起。
He's an awful man - full of his own importance.
He was too full of his own importance to notice anyone else around him.
I worked with her back in the nineties and she had a reputation for being full of her own importance.
She was full of her own importance - you know the type.
See also: full adjective (CONTAINING A LOT)