Take (someone) down a peg (or two) verb phrase
"Take" can be replaced by "bring".
To humiliate someone, or show someone that they are not as important as they think
It's about time that we took/brought Luna down a peg. She is very arrogant!
He was so rude that we need someone to take/bring him down a peg or two.
Anna always boasts about her wealth. I feel sick of hearing her voice; I really want to take/bring her down a peg or two.
Kevin is a bully. We need someone to take/bring him down a peg.
If one is brought down a notch (or two), they are reduced their pride or ego.
To keep reminding someone of their failure or mistake.
To make one become realistic, especially for one often makes a boast
To bring someone down, to put someone in their place, to shame them.
To humble one; to damage someone's ego or pride
The verb "take" should be conjugated according to its tense.
This idiom may date from the 18th century by the British navy. A ship's flags were raised or lowered by a system of pegs. If the flag was raised to the highest peg, it alluded that it was a very important ship. By contrast, when the flag was tied on a lower peg, it implied that it had a less great honor. So when you take someone down a peg (or two), you are reducing or humiliating their ego or pride.