Galatea

Galatea was a clone created by Professor Hamilton from a DNA sample extracted from Supergirl. Worried of the threat that Superman would cause if he went rogue again, Hamilton joined Project Cadmus and developed Galatea for the purpose of protecting humans from the likes of Superman. Cadmus thought it would be able to keep this project under wraps until Supergirl started having dreams of being chased by the military and hunting down those who knew about her. In reality, Supergirl was sharing memories with Galatea as she was hunting down those who knew about her existence. Supergirl, Green Arrow, and the Question tracked her down to Nuvo-Gen, the place where Galatea was created, and confronted her inside a hologram chamber where she attempted to destroy Supergirl until she was caught in an secretly engineered explosion that destroyed Nuvo-Gen. Supergirl, Green Arrow, and the Question escaped, believing that the clone was destroyed.

Professor Hamilton restored Galatea back to health, and with Lex Luthor's recent hijacking of the Watchtower's massive laser cannon to strike directly at Project Cadmus, making it look like it was the work of the Justice League, Amanda Waller ordered her to lead a strike team of Ultimen clones at the Watchtower itself, using special bore-drill missiles to infiltrate the satellite. While the Ultimen kept most of the Justice League members in the Watchtower busy, Galatea headed straight for the power reactor core to cause it to overload. Steel and Supergirl intercepted Galatea at the reactor core to stop her, which led into another fight between the two Maids of Might, with Galatea boasting of her superior strength compared to Supergirl's. As the power core reboot finished and all systems came back on, Supergirl stopped Galatea for good by electrocuting her, using a live power cable and pinning her to a piece of machinery from which she couldn't escape- or so Supergirl believed. How she escaped and her whereabouts since are a story Galatea isn't telling.