The Enemy General (1960)

Allan Lemaire, an American O.S.S. agent, masquerading as a Frenchman, in the Maquis underground during World War Two, is called on to assist the in the escape to London of the heinous Nazi General Bruger, responsible for, among other war crimes, the cold-blooded murder of Lemaire's fiancee and eleven other French hostages. Bruger has bought his escape with the promise of vital information to the Allies. However, it soon comes clear that he has been indulging in a counter-espionage plot, at which point Lemaire, unhappy at having to assist Bruger anyway, provides a vindictive solution.