show (one) who's boss
To demonstrate authority or dominance over one so that it is clearly recognized, especially by means of defeat or some form of subjugation. You can't keep letting your employees walk all over you like that. You need to show them who's boss. You saw what their players said about us on Twitter. Let's go out there and show them who's boss in this conference.
show someone who's boss
make it clear that it is yourself who is in charge.show somebody who’s ˈboss
make it clear to somebody that you have more power and authority than they have: I think it’s time we showed these people who’s boss, don’t you?