Ever since Vegeta appeared in the first arc of Dragon Ball Z, was presented as one of the most powerful villains that Goku has faced. Both warriors were practically immobile after unleashing a brutal battle that left no winner.
After those events, the prince of the Saiyans was left with his pride touched and wanting to widely surpass that rival whom he saw as a low-class warrior.
However, the reality is that Goku, thanks to his training with Kaio Sama, put him at a superlative level that makes him increase his power to heights that Vegeta finds difficult to reach.
The Kaio Ken is the first demonstration of this claim that we are making. After that all the phases of the blond Super Saiyan, the God, the Blue and the Ultra Instinct passed.
Regarding the latter, although Vegeta went for the Ultra Ego, he came after Kakaroto’s divine power; That’s not counting Dragon Ball GT’s Super Saiyan 4, which is not canon.
The only one where Vegeta won.
There is only one transformation in which Goku, until today’s sun, is still behind Vegeta. As the colleagues of Alpha Beta Play remember, the prince of the Saiyans perfectly masters the Ozaru, a technique that with the appropriate adjustments is capable of doing a lot of damage.
When Goku turned into this gigantic monkey, he was just losing control and destroying without knowing what he was doing. In fact, he was not even able to remember what had happened. It was so, unintentionally, he killed his own Grandpa Gohan.
While Vegeta executes it to perfection studying each movement he makes and in this form he almost ends up defeating Goku in the first battle they both had.