Dark Angel

Dark Angel was the Donna Troy of Earth-Seven, rescued from the Crisis on Infinite Earths by the Anti-Monitor to be his Harbinger.  She served the Monitors during the Countdown to Final Crisis and has been a thorn in the side of her counterpart, Donna Troy. 
 
She then tortured Supergirl with unbearable tasks, she forced her to fight against unbearable challenges. Her task was to test the abberations of the universe and she believed Supergirl was one. She hired Batgirl and a Bunch of thugs against her, as well as some ghosts. She made the father box explode and makes Kara see her father, Zor-El. She attempts to destroy Kara by making her believe she was destined to kill Superman. Dark Angel is finally defeated when they meet face to face. At that time, Supergirl was enduring her last test: A fight against another Supergirl… 
From that day, nothing is known about her…