Woah, this is seriously bad-ass! It took me 3 seconds on this page to hit the favorite button. Also, I think her hand, that's resting on the bowbow-mallet is drawn really well (also, sweet bowser hammer). I think it shows really did some serious practice on the hands. Got me a little bit jelly.
Also, the concept on it's own leaves a lot to the imagination, mostly because of the bowser-styled accesories that turned out really stylish and kewl. I can already imagine the fan fics, of peach going mental in bowsers captivity turning into a psychotic-bad-ass.
The only thing I personally don't agree with, is the expression on her face. It's drawn beautifully, don't get me wrong. And I think you can even see that the eyes are in a state of just starting to tear up, if you look closely, because of the way the bottom of the eyes look a bit shiny/bloodshot, but it could be just me looking way too deep into it XD.
With the rest of her face she really has this creepy classic-doll look, wich works really well on it's own.
Though seeing this , thinking about the whole concept, I would've loved to a mix of Harley's mischiefus/evil smile, mixed with peach's kind of pollite and friendly way of smiling.
It's not critisism though, just personall prefference. Though I'm sure it would've reduced my time by half, to hit the fave button. ';p