Vegeta and Nappa came to Earth in search of the Dragonballs, so they could wish for immortality. Even at this very early stage in the saga, Vegeta was tired of Frieza's rulling and wanted him out of the way. After being defeated by Son-kun(Goku) Vegeta vowed to become stronger. On Namek, Vegeta was "forced" to side with Gohan and Krillin to defeat the Ginyu Force. When the three of them were unsuccessful, Son-kun showed up to save the day(again!). Vegeta knew that Goku was unfathomably strong and vowed to surpass him.
When Vegeta was killed at the hands of Frieza, he used the last of his energy to tell Goku of his past of pain. When Vegeta died, Goku very nobelly burried his former rival. There was a time of hopelessness for Goku during his battle against Frieza; however Vegeta spoke to Goku from beyond the grave and gave him Saiyan hope and encouragement.
After being brought back to life with the Namekian Dragonballs, and seeing Goku as a Super Saiyan, Vegeta vowed to reach the legendary level and surpass Goku. When Vegeta discovered that contrary to their thoughts, Goku was still alive after the planet Namek exploded. Vegeta took action. He stole Dr. Briefs' space ship and went out into space in hopes of finding Goku and learning his Super Saiyan secret.
Vegeta returned to Earth unsuccessful in finding Goku. When Frieza Bot and King Cold appeared on Earth, and Mirai Trunks appeared to stop them, Vegeta became even more angry. Not only was this mysterious young boy a Super Saiyan, but he learned in three years, he would perish. Vegeta, and the others, began training.
During Vegeta's training, not only did he and Bulma have a son, but he reached the level of a Super Saiyan. He was out in space, on a planet that, at the time, had fallen victim to a heavy meteor shower. Vegeta gave it everything he had in order to protect his ship. After being sent crashing into the ground, he realized that he didn't care anymore. He didn't care about being a Super Saiyan, beating Goku, or even living. Then something snapped inside of him, and he became a Super Saiyan. By not caring anymore, he thus had pure heart.
Upon his return, Vegeta defeated Andriod 19 with ease. And then, once the group found Andriod 20, Vegeta let Piccolo have some fun. Then, 20/Gero escaped and awoke Juunana-gou and Juuhachi-gou(17 and 18 respectively). After killing Gero, the Jinzouningen twin awoke Juuroku-gou(16) and flew off. Vegeta caught up with the trio and took on Juuhachi-gou by himself. Juuhachi-gou proved to be stronger than Vegeta, and the Jinzouningen proved to be stronger than any of the other Z fighters. Vegeta's pride was crushed
(more to come soon)
