Harley Quinn Pinup

Your coloring is really good, just right for that comic book style. Her face is drawn well and fits the character, you seem to have a good sense of muscle and how it rests under the skin, but you have some problems with the anatomy.

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I did a redraw of how I would have done it. Make of it what you will, but it's just more input.
Her waist is impossibly thin, and to do a pose like that would take a lot of concentration of her part. With the way her waist is, it makes her look pretty flimsy like she's fall over any second, apart from being, like I said, too impossibly thin.

I understand women can be perfectly voluptuous, which is I see what you were going for with her thighs and butt. However the fat distribution throughout her body (of which there is very little.) makes her thick thighs look very unnatural. When making a curvy woman, make sure the fat distribution is realistic.

Her breasts are gravity defying. With the redraw I did, you see that with her being upside down, her breasts should sag downwards a little. Also, while this is popular to do with women in comics, the way her suit fits over her breasts like that just is incorrect. Clothing, even when it's skin tight, doesn't cup over each boob individually like that.
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Fabric rests and stretches over the breasts, rather than curving tightly around it.

Her arms are just a bit too short as well, and her feet are tiny.

I know it's popular to stylize comic book women to the point where they're anatomically not just impossible but ridiculous, but still. I think it's perfectly possible to draw a sexy, attractive woman but still keeping her body proportioned and possible.