Vegito

Vegito is one of the fusion characters from the Dragon Ball game series. He is the immensely powerful result of the Potara fusion between Vegeta and Goku. His voice is a dual voice containing both Goku's and Vegeta's voices. Like his Fusion Dance counterpart, Gogeta, he is regarded as one of the most powerful characters in the whole Dragon Ball franchise.

History
When Majin Buu had all but destroyed the Earth, the only fighters left to stop him were Goku and Vegeta. However, neither was strong enough to oppose him. They used the earrings of the Supreme Kai, the Potara, to fuse as one. This gave them immense power. They defused after around an hour, as the fusion is not permanent if both parties are mortals. Later, Vegito would appear again to fight against the Fusion Zamasu. Potara against Potara, Vegito powered up to the power beyond that of the gods: Super Saiyan Blue.

Trivia

 * Originally, there was little to no explanation as to why Vegito defused in Dragon Ball Z. The reason given was that somehow, the insides of Majin Buu's body forced the two Saiyans apart. In Dragon Ball Super, it was revealed that the fusion is only permanent if one of the parties is a god.