Supergirl. Mary has always been inferior than Billy, except when she had Black Adam's powers. On the other hand I recall reading that Supergirl was supposebly more powerful than Superman, probably BS but still...
What it was was that when she first showed up, she went at full power all the time, so people were comparing her full level to Superman's normal hold-back level.
Both Superman and Wonder Woman have shown the ability to beat her pretty easily.