Eobard Thawne (Arrowverse)

Eobard Thawne is one of the primary antagonists of the CW television series The Flash. He was once a renowned physicist in the 22nd century who had an unhealthy obsession with the Flash. After stealing a time travel device from the Time Masters, he traveled back in time to the 21st century, only to realize that he threw himself into a predestination paradox in which he discovered that he was the Flash's arch nemesis, the Reverse-Flash. This realization drove him insane, and he grew a deep hatred for the Flash. Upon learning the Flash's true identity, Barry Allen, he traveled back in time in an attempt to murder Barry as a child, but the Flash followed him back and prevented him from doing so. Eobard instead killed Barry's mother, Nora Allen, believing that the tragedy would prevent Barry from ever becoming a hero. However, the time jump caused Eobard's connection to the Speed Force to become unstable, and he was unable to return to his time. He stole the body and identity of Harrison Wells, the founder of S.T.A.R. Labs, and created the Particle Accelerator, which malfunctioned and released several unknown energies into the world, causing many people to become metahumans. He planned on training Barry to eventually become fast enough to open a portal that would allow Eobard to travel back to the future, however his plan was foiled by Barry and the S.T.A.R. Labs crew. Eobard was erased from existence after Eddie Thawne, his ancestor, comitted suicide. However since Eobard had heavily modified that world, the universe nearly collapsed as the wormhole reopened as a singularity which also created a breach between Earth-1 and Earth-2. Barry was able to stabalize the wormhole, but Ronnie Raymond and Martin Stein as Firestorm were able to actually stop the singularity, which resulted is Ronnie's apparent death. Since they saved a universe in which Eobard modified, Eobard managed to survive the endeavor, and his consciousness was transferred to Harrison Wells from Earth-2. He did not have full access to Harrison's body, as it was merely his consciousness in his mind, similar to Martin Stein's role as Firestorm. Eobard tortured Wells for several months and eventually convinced him to do what he wanted, as well as slowly taking over Harrison's body and forcing his consciousness out.

The Flash
Eobard appears as Harrison Wells and the Reverse-Flash for the entirety of the first season of The Flash, as well as in flashbacks which showed his transformation into Wells.

In the second season, it is discovered that Wells left a recorded message for Barry in the case of his death in which he confesses to the murder of Nora Allen, allowing Henry Allen to be released from prison. The Earth-2 version of Harrison Wells travels to Earth-1, where he works with the Flash to try to take down Zoom. In reality Eobard forced Harrison to make a deal with Zoom in which he would lead the Flash to his death. If he were to succeed, Zoom would erase Harrison's conciousness from the body and allow Eobard to take over, as well as restore Eobard's negative variant of the Speed Force. Eventually Zoom grows tired of their deal and attempts to kill Wells, however in doing so Wells' consciousness was voided from the body and Eobard took over. He did not regain his full connection to the Speed Force, however he did retain his unstable variant from the first season.

Legends of Tomorrow
Eobard (portrayed by Matt Letscher) appears in DC's Legends of Tomorrow in the future. This version seen in the future has not yet developed Speed Force abilities, and merely shows that Eobard must be alive somewhere.