A Key Event

Spared Z Fighter is the event in The Raditz sub-Saga that alters everything in the canon universe because it is the first saga which precedes Vegeta's and The SSJ sub-sagas. EVERY one of Goku's allies are Z Fighters to a degree. Goku is able to spare his brother's life without having to die himself. Bardock is revived. This goes in depth with Raditz's backstory of the betrayal he went through under Vegeta and Nappa. The world had Kakarot not hit his head that Raditz unknowingly mentions is seen for dramatic irony where Kakarot is picked up by Raditz's alternate counterpart who helps him hunt down the Z Fighter Earthling's alternate selves. It's a foreshadowing of events to come long after Vegeta and Nappa have settled down on Earth.

Main Timeline vs. Canon
Both start out ending Dragon Ball the same way, then diverge in Dragon Ball Z Kai.

Bulma, Chi-Chi, Puar, and Oolong are Z Fighters. This had Raditz and Nappa survived, becoming the 'Butt Monkey' and 'Comic Relief' respectively of the Z Fighters. Raditz starts his new family with Tights after Nappa settles down with Vegeta. Bardock and Gine live nextdoor to Goku. Their crew resides in the new Planet Vegeta ruled by King Vegeta and Queen Eschalot.

Kakarot's World
This Bardock's vision, he and the other Saiyans are never brought back to life. Having ended the life of Son Gohan, young Kakarot meets a teen girl named Bulma. After learning about the Dragon Balls, he follows her all the way to Skull Valley. Bulma protects Turtle from Kakarot whose about to cook him alive. Kakarot, ending up in Aru Village where Bulma retreats to, is the one to defeat Oolong. Bulma praises him but Kakarot brushes off as he continues trailing behind her and Oolong (whose now her new friend) in Diablo Desert. Yamcha and Puar save Bulma and Oolong from Kakarot. They headed to Fire Mountain which Kakarot had destroyed, escaping to Boss Rabbit's Village. The Rabbit Mob was defeated by Kakarot. Their final destination is Pilaf's Castle in which Kakarot transforms into an Oozaru. Bulma and her friends fly away, Kakarot losing sight of their whereabouts. Kakarot seeks out Master Roshi, meeting his apprentice named Krillin. Bulma and Krillin were the only ones Kakarot considered as his friends. Kakarot spends the rest of the time destroying the innocent, awaiting his brother's arrival.

He reunites with his brother, confronted by Piccolo Jr. who distracts them with his Special Beam Cannon to flee. Piccolo Jr. warns the Z Fighters about the Saiyans whom are destroying lives at the moment. Raditz cautions Kakarot about Piccolo Jr. dropping it until Vegeta and Nappa help them take care of everything.

The 4 Saiyans defeat the Z Fighters, having the planet sold shortly after. Vegeta directs them to Namek where they defeat Frieza by their newly SSJ transformations, granting them all immortality.