Super Saiyan 3 is a Transformation that Saiyans with immense power can achieve. It is only achieved by Goku and Gotenks. It was first achieved by Goku who had done it through his years of relentless training in the otherworld.The Super Saiyan 3 form takes a lot of power to maintain. It also takes a rather long time for him to tap into his power to transform. Even Goku had a hard time with it once, and when it uses his time on Earth, it wears him out. In the Dragon Ball Z Raging Blast 2 game in a what-if Vegeta and Broly become Super Saiyan 3. In Majin Buu Saga, SSJ3 Goku was able to punish Majin Buu, even after Base Gotenks, Majin Vegeta, and more had failed. In Dragon Ball GT, while Goku was turned back into a child he once again had ample trouble ascending to this form. He was unable to stay in it for longer periods of time.