Destroyer (2018)

As a young cop, Erin Bell went under cover to infiltrate a gang in the California desert -- with tragic results. Bell continues to work as a detective for the Los Angeles Police Department, but feelings of anger and remorse leave her worn-down and consumed by guilt. When the leader of that gang suddenly re-emerges, Erin embarks on an obsessive quest to find his former associates, bring him to justice and make peace with her tortured past.