Akira Toriyama's massively popular Dragon Ball franchise has always been packed with epic fights, but the all-around best battle in Dragon Ball Z may have been the long-awaited rematch between Goku and Vegeta, this time with a Majin power boost. The culmination of a feud brewing between the two Saiyans ever since the start of DBZ, the showdown was a no-holds barred confrontation that funneled their lost energy directly to DBZ's final major antagonist, Majin Buu, reviving the villain after he lay dormant for years. However, while it was Vegeta that went on to face Majin Buu alone, who truly won the rematch between the two Super Saiyans?
In the seven years since the Cell Games, where Goku heroically sacrificed his life to prevent Cell from destroying the Earth, both Vegeta and Goku had trained diligently to ascend far beyond their previous limits. While both men were capable of achieving Super Saiyan 2 since the showdown with Cell, Goku's natural aptitude to push himself to greater levels of strength and the divine training available to him in the afterlife made him far more powerful than Vegeta. The Saiyan Prince observed their disparity in power during Goku's fight against the villainous Yakon. In order to close the gap with his longtime rival, Vegeta allowed the evil wizard Babidi to possess him through his dark magic, transforming him into the remorseless Majin Vegeta, complete with a noticeable power boost.
Even while Majin Vegeta was able to hold his own against Goku at Super Saiyan 2, it is important to note that Goku was holding back his full potential from Vegeta the entire time. While training in the afterlife, Goku unlocked the Super Saiyan 3 transformation, but chose to remain at Super Saiyan 2, both out of respect to not wound Vegeta's deep-seated sense of pride and because the Super Saiyan 3 transformation would rapidly consume Goku's remaining time on Earth. Evenly matched at Super Saiyan 2, Goku would likely have easily defeated Vegeta had he chosen to tap into Super Saiyan 3 instead.
And while Goku was able to literally knock some sense into Vegeta and convince him to defy Babidi's control and attack Majin Buu, the Saiyan Prince wasn't going to let the rematch end so abruptly without getting in the last word. As Goku moved to get his Senzu beans to heal both men ahead of confronting Babidi and Majin Buu, Vegeta delivered a dirty sucker punch from behind that knocked Goku out cold. Taking the last Senzu bean for himself, Vegeta fought against Majin Buu alone, ultimately dying in his brutal battle against the magical antagonist after realizing that he was outmatched. Goku woke up after Vegeta died, leaving their rematch somewhat undecided, give its inglorious end.
As underhanded as it may have been, a win is still a win, and Majin Vegeta convinced Goku to lower his guard long enough to decisively strike and knock out his rival with a dirty hit. Even Vegeta would acknowledge in the immediate aftermath that their business remained unfinished as Goku lay prone at his feet before turning his attention towards Majin Buu. Goku and Vegeta would get the chance to have a rematch of sorts in Dragon Ball GT and more friendly sparring in Dragon Ball Super, but nothing ever came close to the Goku/Majin Vegeta showdown in DBZ. And even though Goku may have been holding back all along, he was reminded the hard way never to underestimate or lower his guard around the Saiyan Prince.