After fighting Vegeta, Goku spent weeks in the hospital recovering. Over that time, Krillin, Gohan, and Bulma set out to find the Dragon Balls hidden away in a Namek, a far off planet. Using Senzu Beans to recovering, and with a few more in hand, he sets out to find his son and friend and protect them from the danger that is Frieza. During his travel, he communicates with King Kai, who warns Goku of Frieza's might. To prepare for the upcoming battles, Goku uses the ship's artificial gravity.
Once he landed in Namek, he quickly fought off and killed Recoome, one of Frieza's henchmen, allowing him to give Senzu beans to Krillin, Gohan, and Vegeta, who had turned against Frieza. Soon after, they would face the head of the elite Ginyu Force, who swapped bodies with him after seeing Goku's real power level, promoting a fight between Vegeta and Goku that would leave both weakened. Eventually, Goku would outsmart Captain Ginyu and recover control over his body. But before he could face Frieza, he would need to recover, which would take a few hours in Frieza's spaceship.
The battle had already begun by the time Goku was recovered enough to face Frieza. When he came out of the spaceship, he heard Vegeta's last moments, telling the story of how the Saiyans had been murdered by Frieza and his army. Goku, angered, quickly set off to make things right against the Universe's Emperor. Goku fights valiantly, going up to Kaio-Ken x20, a heightened state of battle readiness. But even that is not enough to overpower Frieza, who had only used a fraction of his power.
Frieza then begins to unleash an assault of attack on Goku, quickly debilitating him. Gohan and Krillin attempted to distract Frieza long enough for Goku to set off a Spirit Bomb in a last-ditch attempt. The bomb is successful, but Frieza still lived and quickly killed Krillin and injures Piccolo. Frustrated and angry, Goku taps into a new level of power, Super Saiyan.
Surprisingly, compared to its non-Super-Saiyan counterpart, SS Goku is one of the most beginner-friendly characters in the game's roster. He is powerful but not enough to shine in one single aspect truly. At most, his damage output and space control can be seen as the key feature he brings to a match while also sitting at the lower end of mix-up potential—a great first pick for people that want to learn the underlying mechanics of the game.