The Braggart(1976)

Lieutenant Gilles Castelet would have liked to marry like anybody else. But he has always been under the sexual spell of Colonel Popoti's wife. Once returned to civilian life he tries desperately to escape her, all the more as she is now widowed and she shamelessly chases him away. One day, Gilles meets Charlie, a former army buddy. His friend, sorry about what happens to him, undertakes to rid him of the possession he is under.