The Flash: 10 Best Characters Who Only Appeared In One Episode
5. Clyde Mardon
Clyde Mardon has the distinction of being the first villain this version of the Flash ever faced, and by extension the first metahuman villain in the Arrowverse (give or take the Mirakuru-enhanced Cyrus Gold in the second season of Arrow).
Just before the fateful particle accelerator explosion, Mardon and his older brother Mark (future Flash villain Weather Wizard) escaped arrest at the hands of Joe West and his partner. The aforementioned explosion caused their getaway plane to crash and empowered the brothers with weather-controlling abilities.
This event did not lead the fraternal duo to walk away from crime and they instead doubled down on it. This was especially true for Clyde, whose callous behaviour towards human life and entitlement towards power and influence gave him a god complex of sorts.
Later on he clashed with a rookie Flash and was ultimately defeated by the young hero, who stopped him. Before he could kill Barry, he was shot by Joe, putting an end to his superpowered criminal career before it could get off the ground.