Frieza was introduced as the strongest known warrior in the universe upon his entrance in Dragon Ball Z; this title largely remained in place over time. Even though he would eventually be overtaken, all following villains from Universe 7 were either relics of the past or rivals who developed their might after Frieza was vanquished.
The fact that Frieza was still used to gauge power levels after he passed away speaks something about his legacy. However, Frieza's father, King Cold, is another character from the Dragon Ball universe who might have surpassed him and is hidden in plain sight.
The True Architect of the Frieza Force was King Cold
While Frieza is the front face of his self-titled organization, King Cold wielded equal, if not greater, power from the shadows. As shown in Dragon Ball Super: Broly, he withdrew from Cold Force leadership 40 years ago, with his son taking his place, yet Dragon Ball Z made it apparent that both Frieza and his soldiers still defer to him.
Prior to Dragon Ball Z's "Trunks" Saga, there is no indication that Cold is still alive, with the only mention to his existence being an off-handed comment from Frieza that Goku was the first person to injure him since his father. As a result, the revelation at the start of that arc that his father had joined his son's quest for vengeance against Earth came as a great shock, as well as a significant raising of the stakes prior to Trunks' entrance and fast dispatch of both.
In the manga, the Z Fighters sense Frieza and Cold's power levels and are in awe of both. The anime goes one step further and has Vegeta explicitly state that the latter's ki is even greater than his son's, seemingly confirming that King Cold has been the universe's true strongest warrior the entire time.
Do King Cold's Transformations End There?
What's more, many Dragon Ball fans have pointed out that King Cold appears to only be in his second form. While the series doesn't explicitly confirm whether Cold has further transformations, he looks nearly identical to his son's second form, possessing the same height and tall, curved horns.
Cold matching Frieza in his second form is an impressive feat, especially when considering the gulf in strength between Frieza's second and final forms; his power level going from 1,000,000 to 120,000,000 million upon transformation. Assuming the same multiplier applies to Cold, then that would put him above his son as the strongest in the universe by a significant margin.
It's worth noting, however, that while Cold being in his second form is a popular fan theory, it remains just that -- a theory. So much of the background of Frieza's race and their biology remains a mystery, and until there's official confirmation, Cold could just be in his final form, with a different appearance to that of Frieza's.
What's more, the anime often exaggerates characters' power levels beyond what is established in the manga. Infamously, the Dragon Ball Z anime repeatedly stated that Kid Buu is the strongest form of Majin Buu, despite a plethora of evidence to the contrary in the manga and other sources. As such, Vegeta's statement isn't solid proof that Cold has surpassed his son and can be dismissed as an anime-only embellishment.
Cold Was Weaker Than Frieza, According to the Daizenshuu Guidebooks
There's also the matter of the official Daizenshuu guidebooks, published after the end of Dragon Ball's original run and overseen by series creator Akira Toriyama. The seventh book in the series features biographies of nearly every character in the series, and King Cold's states outright that he is ''somewhat inferior to Frieza''. As frustrating as it may be that this information comes in the form of supplementary material, it's the most definitive answer the series has given so far.
For Dragon Ball fans, power scaling can be a contentious matter. While some debates are clear-cut, others, such as this one, are far murkier. King Cold lacked the influence his son has had on the series due to his brief debut, and even if he was theoretically stronger, he hasn't had Frieza's history as a benchmark of power in the Dragon Ball universe. Regardless matter who was stronger at the time, Frieza has since surpassed his father due to his Golden and Black forms.
No enemy appears to be off-limits in current Dragon Ball. Perhaps Super will one day build on Cold's background as a galactic conqueror, revealing who was the stronger of the two. For the time being, he is but a footnote in Dragon Ball's huge rogues gallery.