Dr. Gero (Jinzoningen #20)

Japanese Names: Doctor Gero (げろ); Jinzōningen Nijugō (人造人間20号)Name Pun: N/AFUNimation Name: Dr. Gero, Android 20Silver Shenron Name: Dr. Gero, Jinzoningen #20Other Names: #20. Cyborg #20. Artificial Human #20Race: Human/AndroidHeight: N/AWeight: N/ABirth Year: N/ADeath Year: Age 767Hobbies: N/AFavorite Food: N/AFavorite Vehicle: N/AFirst Appears: Chapter 337 [Manga], Episode 126 [Anime, DBZ]Appearances: DBZ, DBGTSeiyuu: Koji Yada Voice Actor: Kent WilliamsThis is the mad scientist Dr. Gero, after turning himself into an artifical being. Known as a mad scientist, he was employed by the Red Ribbon Army as a chief weapons expert. Even after the army's destruction, he immersed himself in developing artificial humans in order to get revenge on Goku. Three years after Trunks returned to the future, Jinzoningen #20 (Gero as himself) appeared with Jinzoningen #19. After their initial attack on the city, Jinzoningen #19 and #20 caught Yamcha by surprise, nearly killing the Z-Senshi. Though he's stronger than Jinzoningen #19, he's still considerably inferior to Jinzoningen #17 and #18. Even so, Dr. Gero is truly a genius, familiar with everything from cutting-edge mechatronics to biotechnology.

Even after Jinzoningen #20 was cast into the depths of afterlife, his thirst for revenge lived on. Though Gero died, he left behind his most powerful android that was finished by his computer in the underground portion of his lab, which is his ultimate creation, Cell (Jinzoningen #13, Jinzoningen #14, Jinzoningen #15 as well, if movies are counted).

Dr. Gero is first seen in hell along with Dr. Myu. There, they worked on a plan to create the ultimate android which could destroy Goku. They came up with a plan to combine both of their technologies and get a perfect Android by fusing Jinzoningen #17 and Hell Fighter #17 to create Super #17. They then created a dimensional hole to get both artificial beings in the same place - Earth. During the fight with the Saiyans, he is betrayed by Dr. Myu who commanded Super #17 to kill him, leading to his somewhat ironic death (killed by Jinzoningen #17 again).

An interesting point is that Dr. Gero transferred his own brain into an energy-absorbing model cyborg, rather than an infinite-powered one, like Jinzoningen #17 and #18, which would allow him far greater power reserves that surpass untrained Super Saiyans. This would make Dr. Gero weaker than #17 and #18. Why he chose to be an energy-absorber rather than an infinite-power cyborg is unknown (though #18 hints that it may have been because he thought that an energy-absorbing model android was easier to use as a host).

Somewhat, 3 deaths of Dr. Gero occured in the series.  At first, Jinzoningen #17 impales Dr. Gero with his hand and kicks his head off, then crushes it like a bug (this applies to Super Android 13! as well thus his hatred transfers to his computer, and manufactures Jinzoningen #13 and co.). In Mirai Trunks' and Cell's timeline, Jinzoningen #18 distracts him by knocking over some equipment, and Jinzoningen #17 cuts his head off. As he warns them about Cell absorbing them, Jinzoningen #18 blows up his head. Finally decades later, Super #17 launches an energy wave that blasts Dr. Gero to pieces, this is when he dies again in the present timeline.