Plurk paste

Goku does have another, much darker side to his abilities. While kept at bay by his diadem the majority of the time, Goku's true form is the Seiten Taisei, a powerful being birthed from the aura of the earth itself and nigh unstoppable. As Goku, he is already strong and fast enough to be able to beat most any foe he comes across, but as the Seiten Taisei he is practically invincible. He has been shown to be able to move so fast that he looks like he's teleporting, in one place one moment and right in his enemy's face the next. He's much, much stronger, as well, and has the reputation of single-handedly massacring a large part of Heaven 500 years prior to canon. He can also use the energy of the earth to repair any damage done to him, as seen when Hakkai and Gojyo purposefully remove his diadem in order to keep him from dying. Most terrifying of all, though, is the fact that in this form, destruction is his only goal. He will attack anyone or anything that gets in his way, and will do so viciously and without restraint. ... and this, unfortunately, also includes friends as well as foes. His own friends have been at the end of Seiten Taisei's claws, and afterwards, he always shows extreme remorse for what he's done.

The only thing that can stop him is his diadem, which subdues the Seiten Taisei form and returns him to normal. Sanzo and Kanzeon Bosatsu have been shown to be able to create another one if the original diadem has broken or been lost, but as long as the diadem still exists, it can be placed back on his head to the same effect. Once he's returned to normal, though, he cannot recall anything that happened while the diadem was off.