flex (one's) authority

Translations
проявлять (свою) власть
The manager decided to flex his authority by implementing new rules.
Менеджер решил проявить свою власть, введя новые правила.
Definitions
To assert or demonstrate one's power or control over others, often in a showy or ostentatious manner.
Words
authority

noun
власть
flex

verb
сгибать