Super 17

Super 17 is the fusion between Android 17 and Hell Fighter 17, who is series' second main antagonist and made his debut in the episode "17 Times 2". The episode is a testament to the fusion of the two identical androids.

The Ultimate Android
When Android 17 and Hell Fighter 17 fused, Super 17 was born. He completely dominated Goten, Trunks, Majuub, even Vegeta and Gohan. He had withstood Gohan's kamehameha, and Vegeta's final shine attack. Afterwards, Goku arrived to fight Super 17 as a Super Saiyan. At first, he dominated the beast. But he slowly began to weaken, hit after hit after hit. After firing a kamehameha, Goku realized that a Super Saiyan wouldn't be enough, and thus transformed into Super Saiyan 4. After a number of attacks, Goku realized that Super 17 was absorbing his attacks, and he had to find a way to beat him without the kamehameha. When it seemed the end, Goku wrapped himself around Super 17 to kill himself and take the android with him. But Super 17 puts up a shield to save himself and apparently, it saves Goku from destruction as well. When Super 17 prepares for the final blow, Android 18 steps in, scaring 17 into thinking that 18 will blow up and take him with her. When 18 starts avenging her husbands death with energy bullets, this gives Goku an opportunity to defeat 17 once and for all. He swims through 18's waves and fires Super Dragon Fist. Then Goku fires three finishing kamehameha's at the android, finishing him once and for all.