Tonton Streaming He-Man and the Masters of the Universe (1983) S1E31 - The Mystery of Man-E-Faces

Prince Adam tells Man-At-Arms the story of how he, as He-Man, changed the life of Man-E-Faces. In flashback, we see how Man-E was once a bad guy who terrorized the Widgets with his three faces, and how Skeletor tried to recruit him into his forces before He-Man enabled Man-E to see the error of his ways.