Dark Supergirl is an evil counterpart of Supergirl and a villain in DC comics.
Supergirl faced Lex Luthor in Utah where Lex used black kryptonite on Supergirl. Afterwards, the kryptonite created an evil counterpart of Supergirl, Dark Supergirl. Lex was shocked and confused of the creation of the evil Supergirl. Dark Supergirl heavily severed Lex and began her crime spree. She encountered her good counterpart and they both fought each other.