Black Vegito is the main antagonist at the end of the Zamasu ark in Dragon Ball Super. He first makes his debut in episode 73 entitled: "Dark Potara". Black Vegito is formed when Black Goku and Black Vegito perform the potara fusion during their battle against Super Saiyan Blue Goku and Super Saiyan Blue Vegeta. Black Vegito is the strongest villain in Dragon Ball Super to date.
strength scale: (1-10)
Black Goku (Super Saiyan Dark): 7
Black Vegeta (Super Saiyan Dark): 7
Goku (Super Saiyan Blue): 9.5
Vegeta (Super Saiyan Blue): 9.5
Black Vegito: Beyond 10
Black Vegito is shown to easily defeat both Goku and Vegeta at their maximum. Dark Matter ki allows Black Vegito to over-power gods.
Super Saiyan Dark Edit
Super Saiyan Dark is a future Saiyan transformation. It's gained by using pure evil ki to transform into a Super Saiyan. Such evil ki mixes with the rage creating a dark aura. This is mostly strong in Black Goku and Vegeta, as they have perfect control over their evil ki. Other evil Saiyans such as Broly could not transform into a Super Saiyan Dark, as he doesn't possess true control over such evil ki.
Super Saiyan Dark is known to be the strongest (non-god) transformation and it's ten times stronger than Goku's Super Saiyan 3. This is due to future Saiyan development, such as Goku and Vegeta's primal DNA.
Black Vegito's fusion creates a new ki known as Dark Matter Ki. This ki is stronger than God ki, and Zamasu agrees it's a suitable replacement.