Warning: Wikipedia contains spoilers
In what would later become a trademark of the Rocky franchise, Rocky II starts off right where the first one left. After their championship bout, both boxers are taken by ambulance to a hospital, where they meet once again, at the emergency room. Apollo Creed, the champion, is still angry at Rocky, the first man to go the distance with him, and starts claiming for another chance to knock Rocky out. Rocky, meanwhile, tells Apollo that he is quitting boxing.
Having made more money than he had ever dreamed he could make, Rocky's decision to retire is straightened when the doctors tells him he needs retina surgery, which is a success.
He gets a job as a boxing trainer at Mickey's Gym, and proposes to Adrian,his girlfriend . They get married at a simple wedding ceremony attended only by Mickey, and Rocky buys a two story house in a better neighborhood for her. Meanwhile, Creed had gone to the press giving his opinion that he thought Rocky was a coward for not wanting to fight a second time. The pressure Apollo put on Rocky, which came as a consequence of all the hate mail Apollo was getting at his mansion, started to get to Rocky and he became undecided about fighting Apollo for a second time. He consulted Adrian, but Adrian didn't want him to box again. Later on, Rocky gets a black Camaro and Adrian gets pregnant. During birth, Adrian fell into a coma and Rocky spends his time , standing by her side and taking care of his new son. When she recovers from the coma, she tells him to 'go do it!' and he quickly begins training for the rematch with Apollo.
Next follows a scene where the producers show the audience how Spartan a boxer's training must be before a fight, and then the movie concludes with the rematch fight's scene.
Rocky and Apollo box for 15 rounds, once again fighting an intense battle in front of a standing room only crowd. When round 15 arrives, Rocky seems to be hopelessly behind on points, but, in a scene many Hollywood critics have called one of the greatest scenes in film history, both boxers hit each other with knockout punches simultaneously, and both go to the floor. The referee starts counting, and the count reaches number 10, so in that case, whoever gets up first will be declared the winner by knockout. While Apollo slumps to a corner, Rocky grabs the rope, picks himself up and the fight is declared over, Rocky becoming World Heavyweight Champion.