Le roi des cons (1981)

A former conquest threatens to reveal a Casanova's sex secrets to the world in the French comedy Le roi des cons (1981). Georges (Frances Perrin) has developed a foolproof method that can get any woman he wants into his bed, no problem. Then one of Georges' more enterprising lovers secretly records him in action and uses his techniques to develop a self-help program for guys. Georges is furious that every loser in France now has access to his hard-earned (and now far less effective) game, and he sets out to get revenge--with some unexpected results. Marie-Christine Descouard and Isabelle Mejias co-star as two of Georges' girls and while Isabelle merely bares boobs, Marie-Christine goes fully frontal. Looks like the secret's out!