The Super Saiyan transformations are arguably the most iconic aspect of the Dragon Ball series, though evidently not the strongest as Goku’s most powerful form isn’t a Super Saiyan.
While the first Super Saiyan form was introduced near the end of Dragon Ball Z’s Frieza Saga when Goku unlocked it for the first time and used his newfound power to defeat the evil emperor, Super Saiyan was far from the first Saiyan transformation in-canon. One of the earliest transformations in Dragon Ball history is the Great Ape–a form that debuted during the events of classic Dragon Ball and was revealed to be the go-to transformation for the now-extinct Saiyan race while conquering alien planets. The Great Ape form held raw destructive power that almost no one could effectively combat, especially if there was an army of them attacking all at once. However, that transformation quickly became obsolete once the modern Saiyans unlocked Super Saiyan–which includes levels 1-3 as well as God and Blue. However, upon returning to the original Great Ape form following his mastery of the first three Super Saiyan transformations, Goku discovered a raw power that surpassed anything he’d ever felt before.
Goku’s Strongest Transformation is the Golden Great Ape (& One GT Villain Proves It)
In Dragon Ball GT episode 33 (written by Junki Takegami, directed by Osamu Kasai, produced by Toei Animation), Goku has seemingly returned from the dead following his last fight with Baby, and this time, he is back with a tail. While in the Realm of the Kais, Elder Kai gave Goku his Saiyan tail back as he needed it to unlock Super Saiyan 4. However, before Goku can reach that god-tier form, he first needs to become a Great Ape–but not just any Great Ape, the Golden Great Ape. A Golden Great Ape is a Great Ape made by a Saiyan who has unlocked the Super Saiyan transformation. However, while the Golden Great Ape is reliant on the Super Saiyan form, it is not one itself–though it is necessary to reach Super Saiyan 4. It’s all a little confusing, but basically the Golden Great Ape is a Super Saiyan stepping stone, one that holds unchecked, raw power.
When Goku became the Golden Great Ape while on his way to unlocking Super Saiyan 4, he did more than just rampage uncontrollably–he had Baby-Vegeta running scared. Baby has been named as the strongest Dragon Ball villain in history, and when Baby merged with Vegeta, he became infinitely more powerful. So, for someone as strong as Baby to literally run away from an opponent, that opponent would have to wield unparalleled power. Even when Goku unlocked Super Saiyan 4–a form that should have been stronger than the Golden Great Ape–Baby was still able to land a few punches and overall hold his own. However, when faced with the unadulterated power of the Golden Great Ape, Baby’s only recourse was to run the other way.
To be clear, all this evidence supporting the idea that the Golden Great Ape is Goku’s strongest form is only taking into account raw power and destructive potential, not ‘who would win’. It seems clear that Super Saiyan 4 Goku would be able to beat Golden Great Ape Goku in a fight as he is much more intelligent, but if one were to simply measure the amount of energy emitted by either form, Golden Great Ape Goku would stomp SSJ4 Goku as his inhibitions are completely gone, and he can literally rip a planet apart with his bare hands. For these reasons, it is safe to say that Goku’s strongest Dragon Ball transformation isn’t a Super Saiyan–it’s the Golden Great Ape.