Lots of minor issues pile up.
At first glance there's nothing really horrific about it. But anything more then a fleeting look reveals a lot of minor issues that clog the clarity and impact of the drawing.
I'd like to first mention the hips. It's okay to be cartoony and exaggerate certain aspects of anatomy, however, this needs to be consistent throughout the whole figure. There are certain rhythms of the human body that need to be listened to. Because of the large hips, small shoulders, and large skull, the rhythm is out of sync to how a woman looks.
Second, the face structure is seriously lacking. It's really common for people to try and slap anime features on a flat head shape when drawing in a Japanese style. But this is the wrong way to go about it. Her eyes are facing forward, yet, her head is turned! This suggests that her left eye is right up and close to her ear.
Her mouth was also placed in an awkward spot. She has no jaw, so it looks as if it's been placed under her chin. Look at some skulls to try and mimic where features are placed.
The eyes are also rather lifeless. For a character who is "over-dramatic" you're loosing a lot of feeling by leaving out the pupils.
Next, the armor needs some re-envisioning. There's no way this girl is fighting against a world destroying demon in that. The second she raises her arms those two puppies are falling right out of that breastplate.
She can be gutted, stabbed in the heart, get her legs and arms chopped off, be hit over the head by anything, but at least her shoulders and kneecaps will be alright. You can make sexy work while still covering up her most vital areas.
Last point, the hair. Nothing annoys me more then play-doh hair. What I mean by play-doh hair is that it's a large blob with some spikes pulled out. Pay more attention to how hair falls on the head because it will never naturally clump like that along the bangs.
For coloring the hair, avoid treating it like it's a plastic. There's no need to draw every last strand, but you need to find ways to find a happy midpoint.
Oh dear, that was a pretty long critique. I could go more in-depth, but I think anymore will be counterproductive.
Cheers.