Fans of Dragon Ball Super may not be aware that, while Goku and Vegeta reached a whole new level of power thanks to their Ultra Instinct and Ultra Ego transformation, this also means that their true strongest form will never be seen in the franchise again. The two heroes are developing their strength on two opposite paths, meaning that they will never be able to use the Fusion technique again.
Fusion is a powerful technique shown several times throughout Dragon Ball Z and Dragon Ball Super. It consists of the merging of two separate beings, combining their physical, spiritual, and mental attributes to create a new individual whose power level is higher than the sum of the originals. Fusions are performed in the series through different means. One is the use of Potara Earrings, powerful items possessed by the Supreme Kais, which only require each person to put one earring on. A more complex way is to use the Fusion Dance, a technique that Goku learned from the alien Metamorans. Goku and Vegeta used Potara Fusion to become Vegito, and Fusion Dance to become Gogeta. While fans will debate whether Vegito or Gogeta is stronger, they are both exceptionally powerful. However, both Fusion methods have specific requirements and drawbacks that make them incompatible with Ultra Instinct and Ultra Ego, meaning that Vegito/Gogeta will never make an appearance again.
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The Potara fusion is a technique originally devised for the divine Supreme Kais. Once performed, it cannot be rescinded and the two beings will never return to their original state. This specification only applies to gods: when mortals use the Potara, their fusion will last only one hour.
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