S1·E11 Turnabout

In an effort to prevent Skeletor's evil, Man-At-Arms invents a groundbreaking crystal belt that weakens the villain every time he performs an evil act, or even thinks about doing so. Skeletor is horrified to learn that he can never be evil again, but his Evil Warriors have other ideas. As the heroes believe more peaceful times are upon them Tri-Klops presents to Skeletor a harness, one that will turn He-Man's goodness against him!