Future Son Goku
From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Future Goku appeared in the timeline of Future Trunks and Future Son Gohan. Future Goku makes his only appearances in the brief opening scene of Dragon Ball Z: The History of Trunks on his deathbed and in a flashback in an episode of Dragon Ball Z. Future Goku was far weaker than his main timeline counterpart because he had not achieved any forms beyond the unmastered Super Saiyan form due to the fact that he died six months before the Artificial Humans arrived and killed all of the Z Warriors. Future Goku lived the same life as the main timeline Goku up until his return to Earth after defeating Freeza on Planet Namek where Future Goku used the Instant Transmission technique to return to Earth and successfully killed Freeza and Cold when they arrived in August, 764 Age.
Future Goku contracted an incurable Heart Virus in 766 Age and died six months before the appearance of Artificial Human No. 17 and Artificial Human No. 18, leaving the Z Warriors without their strongest warrior. The Artificial Humans then killed the Z Warriors in May, 767 Age (except for Future Son Gohan (Future Goku's son). Future Bulma, however, determined that Future Goku would have defeated the Artificial Humans had he been given the opportunity, and so she sent her son back in a Time Machine to solicit Goku's help.