Raditz plays a Broly and kills Kakarrotto for his crying.
Serious answer, Raditz probably kills Grandpa Gohan when he discovers the duo in their spaceships, resulting in Galu never having his personality changing amnesia. Assuming Raditz has similar potential to Galu and that his 1200~1500 battle power was due to spending more time in planets with higher gravity as well as possible Zenkais, Raditz is much weaker here, though due to being roughly 5 years older is still strong enough to solo any threats in Part 1 Dragon Ball. So I guess with Raditz's presence as his guardian, Galu gains a great sparring partner which allows him to climb up to levels higher than his 416 BoZ level even without Kami's training, though the two refrain from killing off the human race due to Bardock's command. They still probably kill anyone who resists them, including the eventually released Piccolo Daimao and Majunior, resulting in the loss of the Dragon Balls. Vegeta and Nappa eventually discover them due to Raditz having kept his old Scouter, and the two end up joining Vegeta's campaign to conquer that one tough planet. However, due to the events of Namek not happening as Galu and Raditz would have killed Daimao without making any wishes, they never catch up to the Ginyu Force or Freeza and are forced to serve under Freeza for eternity until Babidi and co. brainwash them and the entire Freeza Force army to use as material to revive Boo.
