Frieza recently proved he is stronger than Goku with the unveiling of Black Frieza, but one DBZ attack confirmed Frieza was always better than Goku.
Even though Frieza has lost to Goku on more than one occasion throughout the course of their Dragon Ball careers, one attack proves to be the perfect metaphor for Frieza’s hidden superiority as it currently stands in the most recently established continuity.
Goku and Frieza first crossed paths on Planet Namek during Dragon Ball Z’s Frieza Saga. In that storyline, Frieza and his army traveled to Namek in search of the Dragon Balls as Frieza wanted to use their wish-granting magic to make himself immortal. However, the Z-Fighters also traveled to Namek as they, too, wanted to use the wish-granting Dragon Balls for their own, less villainous purposes. Eventually, their paths crossed and the Z-Fighters found themselves in Frieza’s crosshairs. Luckily, Goku also went to Namek after he heard there was trouble, and he had become powerful enough to challenge Frieza–and he even managed to beat him. However, the way Goku beat Frieza may ironically solidify why Frieza is actually stronger.
In Dragon Ball chapter 502 by Akira Toriyama, Goku has returned from the afterlife without the use of the Dragon Balls as Old Kai gave the last remaining bit of his life force to Goku so the Saiyan hero could return to Earth and kill Majin Buu before the villain destroyed the entire universe. When Goku arrives at Earth, he doesn’t waste any time and immediately fires an attack against Buu–and the attack he chooses is Destructo Disc. Destructo Disc is an attack that is mostly used by Krillin as it is his signature technique, but here Goku is seen using it against Buu even though Frieza already showed him a similar move that is actually way stronger.
Frieza’s Death Saucer is Better than Goku’s Destructo Disc–Foreshadowing Frieza’s Superiority
Goku was only able to beat Frieza on Namek because he redirected Frieza’s own attack: the Death Saucer. Aside from the obvious differences in color (with the Death Saucer being red and pink while the Destructo Disc is more orange and yellow) the Death Saucer looks and acts much like the Destructo Disc, but it is actually an upgraded version of that technique. The Death Saucer allows one to control the energy discs remotely as opposed to the wild and uncontrollable Destructo Discs.
While Goku managed to be quicker than Frieza’s Death Saucer, leading to the attack backfiring against Frieza and earning Goku the victory, the technique itself is literally an improved version of the Destructo Disc and proved to be incredibly deadly. Basically, Frieza brought a better version of the Destructo Disc to Goku’s attention long before Goku’s battle with Buu, yet Goku still used the inferior version of the technique. This shows that Frieza was ahead of his time in terms of refinement and proficiency in developing the deadliest attacks possible–and that’s why Frieza is currently miles ahead of Goku in terms of power level.
In Dragon Ball Super, Frieza unveiled an all-new form: Black Frieza. While in this form, Frieza one-shotted both Goku and Vegeta while they were powered up to Ultra Instinct and Ultra Ego respectively. With that double-punch, Frieza earned the top spot as the strongest mortal in the universe. While that may have come as a shock initially, it really shouldn’t have. Frieza is a master tactician, a seasoned warrior, and accomplished ruler who understands his power and knows how to make himself more powerful–that’s why he is more powerful than Goku and why, secretly, he always has been. Frieza’s evolution is simply better than Goku’s–something that was shown with Black Frieza, and something that was proven long before that with the Death Saucer, making that one move a perfect metaphor for Frieza’s superiority over Goku in the current state of Dragon Ball canon.