Paradox's Failure Timeline was a possible future that the main timeline was leading toward, one that Paradox himself lamented that if he failed to stop the Time Monster: this would be Earth's 'best' possible future. The event shown takes place in 200 years from now.
In this alternate timeline, Paradox failed to stop his former lab assistant, Hugo, from rapidly aging the world during Paradox. The present Paradox takes Ben to witness Earth's result, where they meet a future parallel version of Paradox, who lamented at his failure to save the world. Paradox took the team back to the accident, where Humungousaur saved Hugo, preventing this future from happening.