In the reality depicted in What if (2nd series) #9, it was not only Thunderbird who died, but all of the X-Men. Both old and new perished in their battle against the mutant island Krakoa, leaving only Professor Xavier and ex-X-Man Beast, who took care of the Professor, due to his depression. When several weeks later, Count Nefaria threatened the world and none of the other heroes were available, the Beast used Cerebro to contact several mutants and teleport them to Nefaria. Among them was James Proudstar, who only agreed to come along as he wanted to meet Xavier and exact revenge for his brother’s death. However, risking his own life during the new team’s battle with Nefaria, James realized that the telepath was not to blame. Just like he, his brother had known the risks involved but he had joined the X-Men of his own free will. Adopting John’s codename as his own, James remained with the new X-Men.
The James Proudstar of the reality dubbed “Professor W’s X-Men” also called himself Thunderbird after his late brother, and he too joined his world’s X-Men. In time, he became attracted to his teammate Nocturne, the daughter of Nightcrawler and the Scarlet Witch, and they started dating. Unfortunately, their relationship came to an abrupt end when Nocturne was snatched away from the timeline to join the reality-hopping Exiles. It is unknown how James dealt with his lover’s sudden disappearance.
In the Age of X, James Proudstar’s family was wiped out during an Exonim sweep of Arizona. He set out to seek revenge for their deaths and killed as many soldiers as he could. The hunters who sought him out called him Berserker and he decided to adopt it as a codename. His half-sister Bethany was used as bait to try and lure him out, but she killed herself rather than endanger her brother.
Still, James nevertheless walked into the trap to retrieve her body. He killed every soldier there and then made his way to the last mutant bastion of Fortress X. The Fortress was under constant attack by the humans but the mutants fought day and night to keep it safe. It was eventually revealed that Legion had created the reality using his god-like powers. The world was put back to the way it should have been and the Age of X was erased.
In the future that depicted The End of the X-Men, Warpath was a member of Cable’s X-Force. When various X-Men villains joined forces to wipe the team out, Cable was one of the many mutants targeted. X-Force was sent to retrieve their leader but their plane was ambushed and it crashed. Warpath survived but was soon assimilated into the Technarx along with the rest of his team.
The Warpath of the Ultimate universe was one of the few mutants who chose not to take the cure when it was offered. He moved to a reservation, named Utopia, in the Nevada Desert along with the remaining mutants. He sided against the group’s leader Kitty Pryde and lived as an outcast for a while with others of a similar mindset. He began a relationship with Psylocke, but that came to an end when it was revealed that she wasn’t who she said she was and that she had been manipulating everyone for her own ends.
Warpath eventually rejoined the rest of the mutants when Jean Grey waged war on Utopia.
In a future depicted in Uncanny X-Force (1st series) #28-29, Wolverine’s method of preventing threats was taken to a whole new level. Now people were arrested or killed the second they made up their mind to commit murder. Warpath was a member of X-Force, which was tasked with locating and bringing in anyone found to be a threat.