I actually continued the rewatch and turns out: Vegeta and Nappa are such egotistical, power-driven idiots that they actively want to kill all humans BECAUSE their offspring might turn out more powerful than them and beat them. Lol. Vegeta is literally the dumbest piece of shit ever, forsaking his entire race in favor of his own power strife.
It's actually amazing what a character arc Vegeta goes through. He's probably the best-developed character in the series, isn't he.
What do you mean? I know all of DB. Instant power up I can think of are: The old wiseman on Namek, although he doesn't give Goku a powerup, only Gohan, Kuririn and Dende. The other one is the Potara ear rings that give you an insta-power up via fusion. You could include the regular fusion here, too, but that at least requires learning the dance.