Pollux (Arrowverse Earth-90)

Pollux was a clone of Barry Allen created to be a test subject for a super soldier. Because of his mistreatment by one of the two people in charge of the research facility that created him, Pollux escaped and learned who he was patterned after, only to later confront his creators and kill them. Ultimately he ended up taking a bullet that was meant for the Flash, sacrificing his life to save someone else in the process.