Ben is from an alternate future two years from the Prime Ben's timeline.
In this Ben's time, Malware was accidentally brought back to life by a very rare electrical storm over Galvan Prime. A loose cable in Malware's containment unit was attracted to the power and it resurrected Malware. Malware's first instinct upon his revival was revenge against Ben Tennyson and Azmuth. Malware ended up like before in destroying Galvan B, but also absorbed every single Mechamorph giving him so much amazing power. After Malware destroyed Galvan B, he went straight to Galvan and abducted Azmuth. Without Azmuth's warning or help, Malware soon kidnapped Ben and stranded him on a planet.
There, Ben watched as Malware used his new found power to enter the core of the planet, then a series of natural disasters caused the planet to be destroyed. Ben became emotionally unstable and enraged at himself and Malware from destroying the planet. Malware ended up being destroyed as well, but it was something he did not care about because he finally had his revenge on Ben Tennyson. Over the next two years, Ben was in self imposed exile on the planet he was stranded on. The trauma and truth of now being the only human in existence continued to plague him emotionally and mentally.
However, Ben may have found a way to go back in time and fix everything and he isn't going to rest until the Earth is again saved. He also does not care how he does it or what consequences it will have on others so long as the Earth is saved from destruction.
Thanks to a time machine Ben stole, he went back in time to prevent his world from being destroyed. He met his past self and told him the horrible future to come, which past Ben was in shock about. Past Ben also learned that his future self became much more serious and didn't care much for protecting innocents anymore. However Future Ben soon learned that Malware of his timeline survived by copying his consciousness inside the Omnitrix. As he learned that, Future Ben headed straight to Galvan Prime without the help of his past self or Rook.
Both Bens even skirmished because past Ben saw that his future self would literally do anything to save his doomed planet. Galvan forces opened fire on him and future Ben squatted them like flies. He makes it to Malware's resting place and narrowly prevents him from being revived. However the future Malware inside the Omnitrix possessed his past self's husk and even used it to possess future Ben. They merge together and become a truly unstoppable force, but past Ben and Rook manage to reach him and they separate from one another. Which caused Malware to revert back to the withered husk he once was and future Malware was destroyed.
With Malware never returned to life, future Ben learned that Earth has returned to where it is supposed to be and he fades away as the timeline re-wrote itself.
Being trapped on another planet caused Ben's hair to grow much more shaggier and he now has facial hair. He has cycles under his eyes because the continued trauma he saw prevents him from sleeping properly. He wears a black jacket over an all green shirt plus a white ascot around his neck.
He is much darker than what he use to be and no longer sees himself as a hero. His failure to help his world makes him a loner and has little care for anyone else or even cares about saving people.