La gammick (1975)

Seasoned drug smuggler and thief François “Chico” Tremblay is tired of his modest lifestyle. Given the opportunity to earn $50,000 killing a prominent New York City gangster, he leaps at the opportunity, ignoring the warnings of Montreal’s leading mob boss, who has forbidden local criminals from taking the assignment. Upon his return, Chico discovers he is being pursued from all sides, prompting an unlikely response: he calls a local talk radio show and starts revealing the mafia’s most carefully guarded secrets. As his revelations get more shocking, so do the tactics of his adversaries, culminating in a devastating gut punch of a finale.