Harley Quinn is, perhaps appropriately, a joke. A tragic joke, to be sure, but a joke nonetheless. She has no combat prowess that would allow her to stand up to Batman in the slightest and without any special Poison Ivy-esque superpowers she’s just a scantily-clad woman. And since Batman is apparently immune to being distracted by the sexy, she’s completely powerless.
Stark Raving Sane 