vigilante
🇺🇸
/ˌvɪdʒɪˈlænti/
🇬🇧
/ˌvɪdʒɪˈlænti/
A person who takes the law into their own hands to fight crime in their community, especially when they believe the police are not doing enough.
The citizens decided to form a vigilante group after a series of burglaries in the neighborhood.