położyć kres czemuś

listen to the pronunciation of położyć kres czemuś
البولندية - الإنجليزية
blow the whistle
To disclose information to the public or to appropriate authorities concerning the illegal or socially harmful actions of a person or group, especially a corporation or government agency

In some jurisdictions, it is illegal to fire a person for blowing the whistle on an employer.

To make a piercing sound which signals a referee's action or the end of a game
(deyim) Bring (an illicit activity) to an end by informing on the person responsible; call public or official attention to something (as a wrongdoing) kept secret ― usually used with on
cause an action or situation to stop by revealing it to opposing parties; blow a whistle to indicate the start or finish of a game or a time-out in an activity