I am Dark supergirl, I and Supergirl fought against each other in Monument Valley, Utah. I exposed Supergirl to the Black Kryptonite ray, but rather than corrupting her as he had expected, the ray actually generated a second, darker Supergirl.

This evil Supergirl possessed all of the normal Supergirl's memories and powers.

Weakness: red sun and kryptonite Resistance: human stuff