In the annals of Dragon Ball history, one of the entries that is certain to be written about the rivalry between Goku and Vegeta is their personal differences. Historians will write that Goku was the nice, easygoing, and friendly branch of the duo, while Vegeta will be chronicled as the surly, hateful, and obstinate opposite. While there’s a reason for these classifications, they are not perfectly accurate. At times, Goku has shown himself to be every bit of the villain Vegeta was at the beginning, at least in of disrespect for his peers.

In one specific instance, Goku's callousness caused immense harm to Vegeta, who had previously been serving as the champion and protector of Earth in Goku's absence. This incident occurs in Dragon Ball Z Episode #169, chapter #391 of the manga which marks Goku's return to the world after training in the Hyperbolic Time Chamber. Before this, Vegeta had been standing in for Goku as the planet's defender.

Goku Tells Vegeta To His Face That He's Lagging Behind

Goku Showed Unusual Callousness in This Instance

After giving his all to defeat Cell, Vegeta's pride takes a hit when his son Trunks emerges as a formidable opponent to Cell. However, any feelings of inferiority toward Trunks are overshadowed when Goku and Gohan exit the Hyperbolic Time Chamber ahead of schedule. After assessing Perfect Cell's strength, Goku its he's no match for the monster, but also refuses to spend more time training in the Chamber. When Vegeta mocks him for fearing the rigors of that space, Goku answers with the most scathing insult possible:

"I've got nothing against you guys using the room, though. You've probably still got room to improve."

When Vegeta angrily asks if Goku is implying to be more advanced than him, Kakarot answers with a mere "Uh-uh. A Lot," before flying away with Gohan, without even giving Vegeta time to reply.

Goku and Vegeta's Relationship Luckily Changed After That Insult

Goku's statement implies that even if he has spent less time than Vegeta training in the Chamber, he has already reached an overwhelmingly superior level. Goku's callous and unnecessary comment crushes Vegeta's pride, especially considering his recent efforts fighting Cell with only his son's help. Goku's response was unwarranted, and this exchange showcases a rare glimpse of Goku's mean streak.

Things are made worse by the fact that, even if Vegeta trains again in the Hyperbolic Time Chamber, he still emerges weaker than Gohan and Goku, as shown by his poor performance during the Cell Games. However, after witnessing Goku's stand against Cell, Vegeta comes to accept that Goku is the better fighter. With his rival gone, Vegeta can finally find peace as a husband and father, in a world that no longer requires his strength for its defense.

However, his recently acquired calmness and resilience crumble when he discovers that, even in the afterlife, Goku has continued training and improving, and has further sured him, reaching Super Saiyan 3. This revelation reignites Vegeta's frustration and causes his progress to unravel. Eventually, this leads Vegeta to give into the influence of Babidi and ultimately become Majin Vegeta.

Luckily, during the Majin Buu crisis, Goku and Vegeta come to once again, fighting together to save the universe. Dragon Ball Super has done a lot to develop Goku and Vegeta's relationship further, showing the latter as a peer on the same strength level rather than a rival always failing to catch up. Still, that scathing remark delivered by Goku before the Cell Games will always stand out as one of the worst insults Vegeta ever received in Dragon Ball history.