One of anime's most beloved characters is the yin to Son Goku's yang, the Prince of Saiyans, Vegeta. Known for his famous arc throughout Dragon Ball Z, as well as his rivalry with Goku, Vegeta has grown leaps and bounds since his introduction during the Saiyan Saga.
There is; however, one more thing the Saiyan Prince can be given immense credit for, and it has changed the landscape of the franchise significantly: the introduction of character-specific transformations. While it was once thought that the path Goku tread in this regard served as the blueprint of the only possibilities, Vegeta's first Super Saiyan transformation opened the door to each Saiyan character's development of their own unique path to power. Here's how.
The Legend
While Dragon Ball is notorious for its lack of consistency when it comes to power scaling, characters' abilities and more, there are certain elements that have remained despite the various changes. Firstly, the Super Saiyan is a piece of Saiyan lore, a legend once thought to be a fairy tale; however, the "Legendary Super Saiyan", or rather, "The Super Saiyan of Legend", Yamoshi, was able to ascend to such a form because of an inherent quality of his that is different to the other members of his race.
Yamoshi was not quite the brutish, power-hungry and murderous type of Saiyan that came to codify the entire race. Rather, he was known as a righteous Saiyan who, when pushed into a corner, achieved the transformation out of a desire to protect. This becomes the basis for what it takes to become a Super Saiyan, at least as far as the Namek Saga and Goku's fated battle with Frieza goes. The legend of Yamoshi proved to be a major motivation for Frieza's eventual destruction of Planet Vegeta, fearing that the Saiyans would one day grow too powerful. This was of course, somewhat retconned in Super when Beerus reveals that the destruction of Planet Vegeta was his will passed onto Frieza.
The Light in the Darkness
Goku's purity of heart is something that has been a part of his characterization since the very beginning, and it is what makes it possible for younger Goku to make use of the Kinto-Un – the Flying Nimbus, which only allows those who are pure of heart to ride it. Goku, Chichi and even Gohan have been seen in various Dragon Ball media making use of it, and this purity of heart follows Goku into his adulthood. It becomes the very basis of his ascension to a Super Saiyan, and his rage at losing his best friend Krillin to a galactic tyrant who also single-handedly ended his entire race becomes the trigger. Vegeta's tearful monologue about the end of Planet Vegeta, the grave injury to Piccolo and finally, Krillin's death become catalysts for a Saiyan just as righteous as Yamoshi to achieve what was once thought to be simply lore.
Goku's anime-only monologue about being "the light in the darkness and the hope of every living thing in the universe that cries out for peace" further strengthens the idea that the initial Super Saiyan transformation emerges in a time of need, when a pure-of-heart Saiyan is put under immense pressure to overcome an insurmountable obstacle. Similarly, when the Super Saiyan God transformation is introduced, it requires six righteous Saiyans to take part in a ritual that infuses their power into one to ascend to godhood, illustrating the franchise's insistence on righteousness as a path to unbridled power. However, that's not the only way.
The Deadliest Sin
What Vegeta's entire character hinges on, at least at first, is his pride in his Saiyan heritage. As the prince of the once-feared warrior race, Vegeta wears his Saiyan Pride like a badge of honour, and consistently denigrates Goku for having no sense of this pride. While it is well-documented that the Super Saiyan transformation initially emerges when its user experiences unparalleled rage, Vegeta's path to this form was a little different.
When Vegeta first becomes a Super Saiyan, it is not out of a need to protect, or avenge; it is borne from his rage at not being able to surpass Goku; his frustration at being unable to reconcile his pride as the Saiyan prince and Saiyan elite with his feelings of envy towards the low-class Saiyan warrior that is Goku. At the time Vegeta also made the claim that his heart was pure: pure evil. Vegeta's pride is vital to his character throughout the franchise, and it is his overcoming of this aspect in certain pivotal moments that makes his arc one of the most notable examples of the infamous "character development", not to mention the old adage, "it cometh before the fall".
The Other Way
Vegeta's placement in opposition to Goku even after his assimilation into the Z Fighters and his famous heel-face-turn is a Dragon Ball staple, as most of Goku's friends are former villains or confused souls. Even Krillin was a little mean at first. Anyway, this opposition or contrast is important because he presents something that the other reformed characters did not: being a Saiyan meant that for the first time ever, Goku's rival was similar to him in biological and neurological composition (obviously, Goku's amnesia and hilarious lack of intelligence or common sense outside of fighting does not apply here). This meant that, finally, there would be someone who could, theoretically, keep up and therefore become analogous to Goku while presenting a thorough, understanding of this composition.
Vegeta understands what it means to be a Saiyan, and has therefore been able to craft a fighting style that incorporates his body's tendencies and an elite Saiyan's temperament. His pride, while having had major negative implications in various crucial moments for himself and everyone else, was a source of power and connection to his extinct people. Vegeta's frustration with Goku is also based on the fact he lacks this inherent understanding of his position as the only other pure-blooded Saiyan left before the events of Dragon Ball Super. Where Goku's path of light is opened by his pureness of heart and his genuinely good nature, Vegeta's path treads the undergrowth and that path is opened up by his unbridled pride in his heritage and himself. Vegeta achieves the Super Saiyan transformation as a project of his egotistical outlook, and actually achieves it, as such, becoming the yin to Goku's yang.
The Self-Taught
Due to Vegeta's desire to achieve what Goku had achieved and be better than him, he centered Goku's path to power and the milestones he achieved. This meant that while Vegeta was trying to establish and assert his superiority, he unconsciously admits his inferiority through his envy, the consequence of which is that his path is then directly influenced by Goku's; thus an attempt to tread where Goku has. With Gohan's ascension to Super Saiyan 2 and the Super Saiyan 3 transformation following in the Buu Saga, the series had clearly created a trajectory for what could be considered battle-ready Super Saiyan transformations.
However, Vegeta's achievement of the Super Saiyan transformation, and subsequent tweaking of the form through its ascended Super Saiyan Second Grade – which boasts more power output at the cost of speed – is evidence of Vegeta's desire to surpass Goku and constantly think of ways to get ahead. Vegeta's autodidactism throughout Dragon Ball Z, and his penchant for mimicry comes in handy as he experiments with his abilities, which then carves a different path for not just him, but the Super Saiyan warriors that have followed in the franchise. When he finally gets to be under the tutelage of Whis and Beerus starting in Dragon Ball Super, Vegeta shows prodigious talent, achieving the Super Saiyan God transformation without a ritual; ascending to Super Saiyan Blue and further evolving it; and even going to Planet Yardrat, where he learned the Instantaneous Transmission and Forced Spirit Fission in less time than it took Goku to learn the former.
Two Infinity
As Goku goes one way – the righteous way; the way of the enlightened – Vegeta takes the darker path. This relationship has culminated in an increasingly different yet comparable path to power for the Saiyan Prince, and for the rest of the Saiyans, who have increasingly tapped into other sources and expressions of power based on themselves as individual warriors. Now that he trains with Whis and Beerus, Vegeta has unlocked a whole new world of power based on his ego, and his Saiyan blood's love for battle, two things that have been integral to the Dragon Ball franchise for a very long time.