During the battle against Vegeta in the Saiyan Saga, Goku managed to pull off Kaioken x4, but this increased output had extremely adverse side effects due to the strain the technique puts on the body.

The Kaioken technique, which Goku learned on King Kai’s planet during the Saiyan Arc, allowed the user to multiply their power levels a number of times over depending on how strong they are.

Kaioken, of course, first appeared in the Saiyan Saga of the Dragon Ball Z franchise, with Goku learning it on King Kai’s planet following his death to his brother Raditz. The “Fist of the ...