From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Future Tenshinhan appeared briefly in "Dragon Ball Z: The History of Trunks" and in "Ghosts from Tomorrow" during a flashback. He was shown outside Future Son Goku's house as Goku died of the Heart Virus. He was later killed by Future Artificial Human No. 18 with a swift punch to the stomach (energy blast in Future Trunks' flashback). He died after [[Future Yamucha] and before Future Kuririn.
Early life and death of Goku
Future Tenshinhan's life was the exact same as his main timeline counterpart's life until the Trunks Saga. In August 764 Age, Tenshinhan watched as Future Son Goku used the Instant Transmission to arrive on Planet Earth and kill Future Freeza and Future King Cold (something Future Trunks Brief's arrival in the main timeline altered). Two years later, in 766 Age, Goku died from a lethal Heart Virus and was unable to be wished back due to the death being of natural causes.
Battle against the Artificial Humans
On May 10, 767 Age, two killer Artificial Humans appeared. Coming to the defense of Planet Earth's inhabitants, Future Tenshinhan and the other Z Warriors engaged the Artificial Humans in battle. Future Tenshinhan was killed by Future No. 18 by a powerful blow to the stomach. The only survivor of the battle was Future Son Gohan, who then dedicated his life to avenging his fallen friends.
- Future Tenshinhan's death differs between the film and the anime. In the film, he is shown in the prologue being killed by a powerful blow to the stomach by Future No. 18. In the anime, he is shown having a hole blasted through his chest by Future No. 18. His true death therefore is debatable.
- Future Tenshinhan is considerably weaker then his main timeline counterpart as he does train vigorously for the arrival of the Artificial Humans as his present counterpart does because he is not aware of their impending arrival.
- Future Tenshinhan is 34 years old when he dies.