My answer would be Power Girl. It's not because she has to compete for a niche with Supergirl.
If you go back to her first appearances, she was supposed to be a (then) modern take on feminine empowerment. She was a different kind of Supergirl, discontent to be her cousin's copy, and unafraid of getting in your face about it. Power Girl was intended to be less an E2 Supergirl than a Wonder Woman For Her Times.
All that had faded away even before Crisis. I suppose is some ways that's appropriate, as her cousin didn't keep his original edge all that long either.