In Future Trunks' timeline
According to Future Trunks in the manga, Future Dr. Gero created Future Android 19 along with Future Android 20, but was killed by the two of them. Future Trunks fought them but fighting alone was defeated.
In the anime, in some flashbacks of Future Trunks' timeline, Dr. Gero is seen as a human after the Red Ribbon Army was defeated by Future Goku, having not made himself into an android. Later in this timeline, Future Dr. Gero (in his Android 20 form) is destroyed sometime after he activates Android 18 and Android 17; Future Android 18 distracts Dr. Gero by knocking over some equipment and 17 cuts his head off. As he warns them about Cell absorbing them, 18 blows up his head. When he is killed, the Supercomputer he made to finish Future Cell is already working, so it continues and eventually finishes its work.
Dragon Ball Super
"Future" Trunks Saga
Main article: "Future" Trunks Saga His soul is later erased along with the future multiverse by Future Zeno in Dragon Ball Super, though his soul still exists in the alternative future timeline created in the anime by Whis warning Future Beerus, and in the manga by Future Trunks and Future Mai using the time machine to prevent Future Shin and by extension Future Beerus' death, which prevents the Zamasu's Zero Mortals Plan from occurring in the new future timeline.
In Cell's timeline
During Cell's flashback to Piccolo, it is explained how Dr. Gero had discovered a way to fuse together the cells from the strongest warriors to walk Earth (Goku, Piccolo, Vegeta, Frieza, and King Cold) and create a supreme fighting entity. After realizing that his project would take too long to be completed before his time, he decided to turn attention to other matters and leave his supercomputer from the lab to complete Cell.
During Super Perfect Cell's flashback, Gero is shown killed by Future Android 17 and Future Android 18. He is killed as he finishes off the settings for the supercomputer to begin working on completing Cell.
Video Game Appearances
- Future Android 20 and Future Android 19 vs. Future Trunks