Reverse-Flash

Eobard Thawne aka the Reverse-Flash is the archenemy of Barry Allen aka the Flash. He was once a wealthy and brilliant scientist from the year 2466 and idolized Barry Allen as the Flash. However, he not only was a major fan of the Flash, he wanted to BE the Flash. He traveled back in time to meet his hero, only to discover that he was destined to be Barry's arch-nemesis. In a fit of rage, he traveled through time to hunt down Barry Allen as a child to erase him from existence, only to be stopped. While Barry saved his younger self from being killed by Thawne, he wasn't fast enough to stop Thawne from killing his mother.

Ever since then, Thawne became trapped in that timeline and while he couldn't age, he still had to live through the timeline all over again.During his time in this timeline, he took out all his hate on Barry's pre-teen years. He left Barry's back door open so his dog would run out and be run over, he pushed Barry down a huge flight of stairs in school and got away before Barry could see anything and in Barry's sixth grade, he was literally Barry's personal boogeyman for a while. He made Barry look crazy and made sure he had a bad childhood. He took over S.T.A.R. Labs where he made sure that Barry would become the Flash so that when Barry became strong enough, he could kill him and travel to the future where he would become the only Flash.

He was a member of the Rogues led by Captain Cold, however, he betrayed them afterwards. He is a founding member of the Legion of Doom and the Injustice League.