The Legionnaires: White Witch
The White Witch, aka Mysa Nal of Naltor, aka the Hag, Xola Aq, Jewel, the Black Witch. Created by E. Nelson Bridwell and Curt Swan.
It seems like Paul Levitz was the only one who ever knew what to do with the White Witch. Originally she was a walk-on character, a minor villain retconned into being Dream Girl's long-lost sister. Levitz saw potential, though, and made a full-fledged Legionnaire out of her. Mysa had a gentle and diffident personality (which made her easy to underestimate, as her character was a lot stronger than her ethereal-albino image suggested) and a tentative semi-romance with Blok. Unfortunately, every other Legion writer has felt it necessary to give her some kind of dysfunctional relationship with Mordru, which isn't any fun (except for Mark Waid, who turned her into Mekt Ranzz's personal teleporter).
What Levitz did best with Mysa is to manage her use of magic. Fantasy writers come acropper in their use of magic more often than in any other part of their writing. There's no mistake easier to make than figuring out how magic works in your particular story and then allowing your main character to go ahead and use it just how it works. At which point, of course, he or she is omnipotent, and your story stops being interesting. Levitz didn't do that, though; he found the same solution that the creators of Dungeons and Dragons did: Mysa can do pretty much anything with her magic, as long as she gets it ready ahead of time.
Compare Mysa with Zatanna. Zatanna can basically do anything, except when she can't (because someone knocks her out before she can yas eht cigam sdrow, or gags her, or something similarly farfetched); Mysa can't do anything, except when she's ready to do that specific thing. Much more satisfying and elegant.
Here are the results: the White Witch, plus prep time, versus a Khundish warrior who has already mowed down Invisible Kid, Wildfire, Dawnstar and Blok without breaking a sweat. From LSHv2 #299 (Levitz/Giffen-Mahlstedt):
Take note of her little smile and her stance. She may look like a fairy princess, but she's a gunslinger. That's the Mysa I want Paul Levitz to bring back; none of this Black Witch flummery.