The Incredible Hulk #156

Hulk arrives on Jarella's world with the mental acuity of Bruce Banner. He finds the city of K'ai in ruins and discovers that Jarella has been captured by the treacherous Lord Visis. Hulk rescues his lady love and leads her people in revolt. That is, until Visis teams up with master assassin Krylar who has a weapon that makes one battle one's darkest fears. The weapon is turned on the Hulk and Hulk with Banner's mind finds himself facing his old brutish self. Jarella's magicians counter by ending the spell that makes Hulk smart. Pym's serum wears off and Hulk grows back to normal size.