S1E18 Twin Streaks (1)
Barry is cloned by Dr. Jason Brassel, who names the clone "Pollux". Upon learning he has created for the purpose of weaponization, Pollux goes on a rampage and comes into conflict with the Flash, ultimately defeating him. Brassel attempts to kill Barry to cover up his own tracks, but Pollux takes the bullet and dies in Barry's arms, while Brassel succumbs from the injuries Pollux had earlier inflicted on him.
First Air Date: 04/13/1991