After killing the dragon of four stars (Suu Shenron) Li Shenron appears (the dragon of one star and also the leader of the evil dragons and the strongest).
Li Shenron can control Goku ( Super Saiyan 4 form) without problems. Goku uses his most powerful technique, the Kamehameha increased 10 times. But Goku was defeated by Li Shenron.
Goku would be killed by the dragon, but Gohan, Goten, Trunks and Uub appear (they save Goku). In an act of extreme difficulty, Goku asks his friends to pass the energy for it. Goku returns to the form of Super Saiyan 4, but this time with much more energy. Goku can defeat the dragon (Li Shenron is hit by a powerful blow). But this powerful coup from Goku was not enough to defeat Li Shenron.
Li Shenron eats the dragon balls. Li Shenron becomes Omega Shenron. Omega Shenron acquires a unique power and wins easily.
Goku (with no choice) tries to commit suicide with the enemy in an explosion. However Vegeta appears. Vegeta becomes Super Saiyan 4 (Vegeta is using a machine with Blutz radius). Goku and Vegeta (both transformed into Super Saiyan 4) use the fusion.
Omega Shenron was almost defeated, but the time of the fusion is over.
After a long battle, Omega Shenron defeats Goku and Vegeta. Omega Shenron is destroying the Earth. However Goku appears. Goku decided to make the Genki-Dama (the Genki-Dama is made with the energy of all beings in the universe). The Genki-Dama universal is released and Omega Shenron is eliminated permanently forever.