Okay, so I'm running a bit late on this one, but here it is at last.
There is a difference between costumes that are merely inappropriate - either not suited to the particular person wearing them (although they might look fine on someone else) or to the setting of the story (eg. space suits that include either miniskirts or bikinis) - and the truely disasterous that would look hideous on anyone.
Flower from Kamandi wears a torn red skirt and no top, and appears to have her long hair stapled to her chest. While this is entirely consistant with the circumstances of the story, you have to wonder why Kirby chose to have a female character running around topless in a comic where sight of a stray nipple would be strictly forbidden, requiring such a clumsy device to keep her decent.
A typical way of showing when a good female character has gone bad is to put her in some kind of bondage/fetish costume. A prime example is Sue Richards of the Fantastic Four, whose repressed urges were released when she donned the fetish costume of Malice. It is actually a very good story empowering the Invisible Woman, unlike the semi-sequel where the return of the Malice persona is signalled by Sue taking a pair of scissors to her regular costume and cutting a lot of holes in it, and then biting the head off anyone who comes near her.
Costumes with only one pants leg never work, even when drawn by Alan Davis.
Not many comic characters could pull off a tailcoat and fishnets, but Zatanna only works if that is what she is wearing. As a stage magician it is entirely consistant for her to wear such an outfit and it's only when they try to make her look more superheroey that it all falls apart. In the recent mini-series Grant Morrison puts her in a variety of absurd cheesecake outfits but they work because they look like stage costumes, wheras the two she wore while an active member of the Justice League completely jar with her personality.