La contre-attaque

Omega Shenron blasts everyone except goku away. Goku counterattacks, but he was not able to inflict any damage at all. Omega Shenron retaliates by using the powers of the four, three, six and five star dragons. At this point, Goku, whose vision has been restored, blasts a Kamehameha at Omega Shenron who was taken by surprise, and seemingly destroys him with a Dragon Fist. However, he regenerates back to normal using the power of the five star dragon. Omega Shenron's power has far surpassed Goku's. Goku is no longer a match for him. Desperate, Goku grabs Omega Shenron. He begins to self-destruct, but Vegeta arrives and tells him not to. He knows firsthand that self-destruction doesn't work. Bulma arrives with the Blutz Wave Generator, and she blasts Vegeta with it. Vegeta transforms into a Great Ape, and it seems like he has lost control of himself, but he quickly becomes conscious of his actions. He then transforms into a Super Saiyan Great Ape and finally Super Saiyan 4, but even teaming up with Goku won't be enough to stop Omega Shenron. He suggests that he and Goku fuse together. (Source: Wikipedia)