Android 21

*DISCLAIMER*- All my work is edited with photoshop using existing pictures.

In an alternate time line, Cell was too powerful for the Z Fighters to handle. However, this version of Cell did not obey Dr. Gero's orders and went rouge; trying to destroy everything instead of getting revenge for the deceased doctor. Gero anticipated such an occurrence and created a failsafe in case Cell turned against him: Android 21. This android was created using the DNA of Goku and Vegeta (effectively making him a saiyan). And was made with properties from both the absorbing androids and those with inexhaustible power sources (#17 and #18). This android absorbs any kinetic energy applied to its body and converts it into its own power supply. The energy he absorbs never depletes, making him permanently stronger with each blow he takes. His energy cell's maximum capacity grows slowly over time (based on how much energy he absorbs). However when the cell is overcharged, the excess energy must be purged from his body, or he risks being destroyed. When the Z Fighters destroyed Gero's lab, the blast supplied enough energy to awaken #21 and destroy the capsule containing him. He seemed to be unaware of his being an android, and had no memory of Dr. Gero. After some persuasion, he decided to help the fighters destroy Cell. However, it was almost too late, as most of the Z Fighters had already been defeated.
Every one of Cell's attacks only served to strengthen Android 21; who continued to dominate cell until finally destroying him with his signature move: Crimson Barrage. Cell regenerated, twice as strong as before because of his Saiyan DNA, and launched his Solar Kamehameha at #21. At first, the energy seemed to overwhelm the android but he became hyper-charged by the blast, and reached his super form. In this form, Android 21 gained full use of his power source, making him unimaginably strong. Cell tried a more direct approach, landing several powerful blows on #21. However, none of the hits seemed to have an effect. Cell realized he was no match for him, and tried to self-destruct. But before he could gather the energy needed to blow himself up, #21 delivered a massive punch to his stomach, causing him to regurgitate Android 18 and revert to his semi-perfect form. He then proceeded to obliterate Cell with a new, extremely powerful move: Crimson Flash. With Cell defeated, the Z Fighters gathered the Dragon Balls and wished back the people that had been killed. Android 21 stayed and trained with them, despite already being more powerful than even Gohan (who had reached ssj2).