So apparently in the new Dragon Ball Heroes anime an evil saiyan is going to be resurrected by a character named Fu. Who is Fu in Dragon Ball Heroes?
Fu is a character who made his debut in Dragon Ball Xenoverse 2. He is a mutation of the 2 main Antagonists of the game, Mira and Towa. He comes from the Demon Realm and was considered to be Dabura's successor, (Note: Dabura is the same Demon King from Dragon Ball Z whose sister happens to be Towa).
Despite being an antagonist and having a rather evil appearance, you couldn't necessarily call him evil. He is a very powerful being and inherited his power from Mira and at the same time, he also inherited Towa's intelligence, hence making him very interested in science.
He was originally created in Dragon Ball Online and made an appearance in the guidebook, however, his first debut is in Xenoverse 2 in the latest DLC. You can find out more about the character by playing Fu's arc in the game.