What's the videogame equivalent of this moment?

Why didn't Frieza kill Vegeta a long time ago? He wiped out most Saiyans but spared Vegeta?

>be Vegeta
>spend your whole life obsessed with power and becoming the strongest you can
>have a power level of 18,000 after decades of training, conditioning and pursuing strength
>still pale in comparison to the likes of the Ginyu Force
>get beat up once or twice
>suddenly eclipse the Ginyu Force and can even tangle against Frieza's low level forms, something no one else in the universe could do before

Why don't Saiyans just beat the shit out of each other to trigger Zenkai boosts instead of wasting time training? Turns out any Saiyan could have gotten within Frieza's ballpark after a couple of self inflicted ass whoopings

(Also why Zenkai boosts are the dumbest fucking addition to this franchise)