Eobard Thawne (Earth-1: Pre-Crisis)

Professor Eobard Thawne (born c. 2151) is a speedster from the twenty-second century and an archenemy of The Flash.

Early life
Eobard Thawne was born in the twenty-second century as a descendant to Eddie Thawne and Agnes. In his childhood, he was taught astro-navigation and became a physicist in his adulthood. With the knowledge, he built a suit that is similar to The Flash suit. At some point, he started to idolize him.

In his research, he discovered the accident of The Flash and recreated it in order to gain superhuman speed. He later learned about The Flash and time-travelled back in time where he found out that he is the archenemy of The Flash. He grew to despise the hero he admired and tied to become the opposite of The Flash at all cost. To make sure that happens, he created the Negative speed force using negative emotions and used it to travel across time. Since then, they battled against each other for years and neither are fast enough to defeat the other.

After learning about the secret identity of The Flash by travelled back in time to 2016, he got the help from The Flash himself to travel across time. Eventually, it led to the Crisis. During the time, he learned about the secret identity of countless villains and heroes.

Original timeline Crisis
In 2024, Eobard fought against The Flash and other legendary heroes. However, they both vanished and time-travelled back to March 18, 2000. They both fought against each other and Eobard attempts to kill the younger self of The Flash. However, the future self of The Flash took him away and Eobard decided to kill Nora. However, the time-travel drained the energy of Eobard and he was stranded in 2000.

Later, Eobard followed Harrison Wells and caused a car accident on him. Harrison was heavily injured and Eobard told him about his accomplishment. Eobard later used a futuristic technology to steal his appearances as well as impersonating him. Later, he was pulled out from his car and was mistaken as Harrison Wells.

As Harrison Wells
As Wells, Eobard was dedicated on creating the S.T.A.R. Labs particle accelerator. He later used past knowledge to ensure his plan works and set up cameras across Central City. To avoid the attention of the Time Wraiths, Eobard took precautions on altering the timeline.

S.T.A.R. Labs particle accelerator explosion
On December 11, 2013, Eobard held an event to celebrate the activation of the particle accelerator. Marlize DeVoe later asked would the accelerator wrk perfectly. Remembering the DeVoe name, he realizes that Clifford DeVoe is also present and told him about him admire DeVoe's work, hinting the later events.

During the activation, he noticed that Barry and Nora arrived in the time vault and he tried to investigate it only to be stopped by Cisco and Caitlin.

The accelerator later exploded like it originally did and gave powers to thousands of people including Barry Allen, who returned from Starling City and was cleaning up his lab at CCPD. Eobard later faked on being paralysed in the accident which is also a way to charge his speed.

Trivia

 * Currently, he is the arrowverse most recurring villain to have appeared as a crossover antagonists and as a main villain for both The Flash and DC's Legends of Tomorrow.