Kaio-ken x20 (20倍界王拳 Nijūbai Kaiōken), also called Maximum Kaio-ken (最大界王拳 Saidai Kaiōken) is the strongest version of the Kaio-ken.
Goku uses this technique against 50% Power Frieza on Namek, unleashing a Kaio-ken Kamehameha, however Frieza stops the technique with just one hand.
Goku later uses this technique on top of the Super Saiyan Blue form - resulting in the X20 Super Saiyan Blue Kaio-ken - against Jiren during the Tournament of Power, however he is still no match and is knocked down.
Video Game Appearances
In Dragon Ball Online, the Earthlings, Namekians, and even Majins via mimicry have the ability to go Kaio-ken x20 and even higher, never seen in previous uses by Goku in the original series. The only increase that comes with multiplying the Kaio-ken buff is the chance of critical strike; for example, activating it doubles the player's critical strike, and the following multiplication would put the increase at x3.
Same as Dragon Ball Online, the Xenoverse series has the same races, while exclusively adding in the Frieza Race, can also use Kaio-ken x20.
Maximum Kaio-ken was named in Dragon Ball Fusions and is depicted as the strongest version of the Kaio-ken in Dragon Ball Fusions. It can learned by Saiyan beyond God Goku, GT Goku at Level 65, Goku (Super) at Level 70, and Super Saiyan Blue Goku at Level 85. It can also be learned by several other playable characters such as Garatz, Baba G, Peperon, Halto, and Uzma. When used it grant the Kaioken+ status to the user which decreases their defense while increasing damage to enemies times 2 for the next turn.
- Unused voice lines in Xenoverse 2 indicate that Krillin and Yamcha can use the Kaio-ken x20.
- While Super Saiyan 4 Goku appears to be using the Maximum Kaio-ken in trailers for Dragon Ball Fusions he is actually using a different Special Move called Maximum Charge and Maximum Kaio-ken does even appear in his list of learnable Special Moves. It should be noted that GT Kid and Super Saiyan 4 Goku appear as separate playable characters each with their own separate movesets in Dragon Ball Fusions.