Reverse-Flash, a.k.a Professor Zoom, is a premier skin for The Flash in Injustice 2. He is classified as a Gadget user. Reverse-Flash relies entirely upon his speed to fight, literally running circles around slower opponents.
Eobard Thawne was a fan of Flash's from the future, who replicated the same experiment that gave Flash his powers. After traveling back and learning of his destiny as the Flash's nemesis, he sought to ruin Barry's life, due in part to the fact he cannot kill him without creating a time paradox. One of the worst acts he committed was killing Barry's mother.
He is trapped in the past because the Regime killed one of his ancestors, and he joined Grodd's Society in vengeance.
With help from Deadshot and Captain Cold, he attempted to kill Barry but failed.
Below are the two skins of The Flash pertaining to Reverse-Flash.