In fact, the protagonist can kill Frisha and his brother Kevela when he is a teenager, and Frieza's strength is only 1/3 of his brother, and killing him is like twisting a bug to death, which is really meaningless. Moreover, Son Goku will become a Super Saiyan largely thanks to Frieza, who will not be really angry if he does not die, so as to become a Super Saiyan. So this plot is not easy to change, of course, the protagonist will increase his chances of shooting later.