Hulk and the Agents of S.M.A.S.H. - Season 2 Episode 13

Upon S.H.I.E.L.D. exonerating them from the frame-up in Vista Verde caused by the Agents of C.R.A.S.H., the Agents of S.M.A.S.H. track the Leader to a deserted island. They get stuck in a deadly maze (which Leader improved on Thunderbolt Ross' plans in his earlier fight with Hulk) where Hulk's rage is drained from him, making him mellowed out. After the rest of his teammates are captured, Hulk finds them in Leader's clutches at the center of the maze where Leader uses his machine to manifest Hulk's dark side in the physical form of Dark Hulk.