Having his potential unlocked by Grand Kai meant that he gained access to "all" his power, so going Super Saiyan wouldn't do anything for him while in his Ultimate form. The Super Saiyan form can't bring out any more of his power if he's already using it.
Later, during Frieza's revenge, Gohan is revealed to have lost most of his power after giving up fighting to focus purely on his education (though he was noted to still be stronger than Piccolo).
Would Gohan have been stronger than Goku if he kept training?
Gohan always had the most potential out of all the Z-Fighters, but his lack of training and commitment always hindered his growth, while Goku instead keeps getting better. According to Piccolo, however, Gohan can still surpass his father.
Gohan was planned to be Dragon Ball Z's main hero but was ultimately replaced by Goku due to popularity and story structure. Toriyama wanted Gohan to take over, but fans preferred Goku's heroic antics and the series' focus on his adventures.
What If Gohan NEVER Stopped Training? FULL STORY | Dragon Ball Z
Is Gohan canonically stronger than Goku?
After enduring Old Kai's antics for over 25 hours, Gohan finally awakened his Ultimate form, also known as Mystic Gohan, making him easily stronger than any of the other Z Fighters (Goku included).
Gohan had to get weaker in Dragon Ball because of how much getting stronger had hurt someone he loved, but now he reclaims that same strength to protect his family, which makes the story come full circle.
until Gohan accumulates an immense amount of Ki and manages to deliver a powerful blow to his father's stomach. Many have taken this single, precise punch as a sign that Gohan Beast has not only mastered his Beast Mode, but also surpassed Goku Ultra Instinct.
Gohan is officially declared the strongest hero in Dragon Ball by series creator Akira Toriyama. Gohan's Beast transformation has made him even more unstoppable, surpassing Goku and Vegeta. Beast Gohan's return in Dragon Ball Super is highly anticipated and fans hope he will play a role in future arcs.
This was true with him being the first to go Super Saiyan 2 against Perfect Cell as well as unlocking his Ultimate/Potential Unleashed form, which was even stronger than Super Saiyan 3 Goku at the time of its introduction. So, when it comes to asking whether Gohan can surpass everyone, the answer is absolutely.
Goku's Grandpa Gohan Made Peace With His Death Long Ago
The main reason that Grandpa Gohan is never revived via the Dragon Balls is that he's made peace with his death and rather enjoys the afterlife. This was made clear to Goku when he fought Gohan during Fortuneteller Baba's tournament.
It mainly boils down to his training. You see, unlike Present Day Gohan, Future Gohan didn't receive the same amount of training needed, to properly prepare for The Androids. That's why he's so weak, during the Future Timeline.
Gohan then carries the unconscious Trunks while trying to find a place to hide. He is successful in hiding until the androids decide to bomb the entire area in hopes of driving them out. Gohan manages to protect Trunks and stay hidden, but at the cost of his left arm, which is completely blown off in the bombing.
Gohan's new transformation is called a "singular talent" unique to him, surpassing even his previous Ultimate Gohan state. Gohan's Beast form may be on par with or even surpass Ultra Instinct, making him a valuable asset in future battles.
Dragon Ball's Goten has always been a powerful warrior and has proven time and time again that he is just as strong, if not stronger than his elder brother Gohan. With his seemingly limitless potential and eagerness to fight, it's very possible that Goten could end up becoming the most powerful Saiyan ever.
That's the question raised by Gohan's sound victory over Frieza in Fusion Reborn, as it not only proves how much Gohan surpassed his father at that time, but it also indicates that Gohan may be the only Dragon Ball warrior strong enough to eventually take down Black Frieza.
Gohan reaches his ultimate transformation in chapter 99 of Dragon Ball Super, finally making the Saiyan's peak form from the movie fully manga canon. The concept of Ultimate Gohan actually foreshadows Gohan's mindset during the Tournament of Power.
Gohan's lifetime of battle experience and training, as well as a more controllable and sustainable transformation, gives him an advanage, but Broly has the potential to surpass him.
With his potential for power and understanding of the heavens, it's not a stretch to say that Goten may be the true successor to Ultra Instinct and eventually fulfill his destiny as the ultimate warrior of Dragon Ball. Goten's name and abilities suggest that he is destined to be the true successor of Goku.
Gohan Beast is allegedly stronger than Goku, who Dragon Ball has also implied is stronger than God of Destruction, Beerus. Gohan Beast may be stronger than Beerus, but he lacks the experience and killer instinct to defeat him, especially since Beerus has deadly attacks like Hakai at his disposal.
A scientific basis for this could be that since both Vegeta and Goku married humans, the trait became recessive, and Gohan just so happened to have inherited it, while Trunks, Goten and Bulla didn't grow them.
In Dragon Ball Z: Resurrection 'F'/Dragon Ball Super, having since retired from fighting completely and slacked off in his training, Gohan became very scrawny in build.
Old Kai released Gohan's power. Goku stated that he was "stronger then he ever was as a Super Saiyan". Thus, his base power exceeded the power he had previously shown as a Super Saiyan and Super Saiyan 2, and thus at the time he had no need to go Super Saiyan.
