Goku learned Kaioken from King Kai and increased his power ... Although Gohan was the first Saiyan to achieve the SSJ2 form ...

In the series, Goku uses it as SSJ and SSJ2. Kaioken was created by North Kai, and only Goku has learned to use it. Even though other characters trained with Kai in the Other World, no one else ...

While fighting Hit, Goku decided to use Super Saiyan Blue with the Kaioken on top of that, mostly called Blue Kaioken, thus giving him a massive upgrade in speed and strength. This was also used ...