Uub

Uub appeared at the very end of Dragon Ball Z during the 28th World Martial Arts Tournament. Goku noticed the boy's unusual power and deliberately provoked him by insulting his family, drawing out Uub's hidden strength. Impressed by what he saw, Goku announced that he would leave to train Uub personally, departing with the boy to his remote village. This scene served as the series' epilogue, suggesting that Goku had found a worthy successor.

In Dragon Ball GT, Uub appeared as a fully trained teenager who had spent years studying under Goku. Despite his training, he found himself outmatched by the threats of the GT era. During the Baby Saga, Uub fought the Tuffle parasite Baby but was overpowered. In a desperate gambit, he merged with Good Buu, creating the fusion warrior known as Majuub. This combined form blended Uub's disciplined fighting technique with Buu's magical abilities and regeneration.

Majuub proved to be a significant upgrade, capable of holding his own against powerful opponents and using abilities like the Chocolate Beam inherited from Buu. He fought against Super Baby Vegeta and later against Omega Shenron, serving as support for the primary fighters. While Majuub never achieved the top-tier status that Goku's endorsement seemed to promise, he remained a valuable and reliable ally throughout GT's run.

In the Dragon Ball Super manga, Uub appeared during the Galactic Patrol Prisoner Saga. When the Grand Supreme Kai's dormant power within Good Buu needed to be transferred, it was ultimately channeled into Uub, connecting him to the ancient divine power that predated even the current generation of Kais.

Uub's power comes from his nature as the positive reincarnation of Kid Buu. All of Buu's enormous power was compressed into a human body, giving Uub a theoretical ceiling that rivals the strongest fighters in the universe. However, unlocking this potential requires extensive training and emotional triggers, as the power is dormant and emerges primarily when Uub is angry or desperate.

After merging with Good Buu to become Majuub, Uub gained access to Buu's magical techniques, including the Chocolate Beam, shapeshifting, and enhanced regeneration. He could also channel massive amounts of ki into concentrated attacks and possessed stamina that far exceeded normal human limits. The fusion was permanent, unlike the time-limited Fusion Dance, making Majuub a consistently available asset.

Uub represents one of the franchise's most compelling unfulfilled promises. Goku identified him as the fighter who could eventually protect Earth in his absence, and his connection to Buu gives him a unique spiritual lineage. Whether future Dragon Ball stories will fully realize Uub's potential remains an open question that fans continue to debate.