King Cold

Uh, in Dragon Ball Xenoverse II, Lord Slug is shown to be aware of the existence of Majin and their do- demonic nature, having heard about their, all their planets destroyed by Majin Buu.

Cooler is shown to be aware of the existence of Majin Bu- Buu as he has been warned about them, uh, by his father, King Cold.

Several comments made by various characters in different Xenoverse series implies that other Majin besides Kid Buu may have existed in the past.

Hmm.

Halfway through our answers.

Number six, who kills Frieza and King Cold? With an assist from time travel, the answer is Trunks.

Trunks.

Question number seven, who is Goku's older brother who tries to recruit him in conquering other planets? That Goku sibling is Raditz.