In General the drawing looks nice, although i have to mention some flaws.
But first let me adress the good points:
-The Pose is interesting and looks pretty interesting
-A lot of detail and effort went into it and that shows ^^
-You can instantly see what character this represents and that's great
But, i have some things to say:
First of all, you can clearly see you had some trouble lining the entire drawing, my advice is to be a bit looser with your lines, you learn a lot more from sketching 2.
Also, despite the nice arm coming towards the front, the drawing lacks a bit of perspective, for example, the headpiece Mercy is wearing doesnt fit properly, nor do her wings. Best way to fix this is to pick draw some lines horisontally when you are sketching so you can line up the wings etc.
I know im giving alot of tips but in my opinion thats the thing you learn the most from, becuase with "omfg its so good" you rly don't learn anything.
Also, make sure the hair is one piece, its clearly stacked up right now, just dont draw the lines all the way, if you do that the problem is fixed.
And, make sure NEVER to draw the bottom of the nose with one line, it are speperate holes, try using an example for the nose, it really helps.
I got a couple more things about the face, make sure to make the outlines of the face clear, as in, where her jaw is, where her chin is, it will make everything look a lot more solid. Make sure the eyes aren't like those egyptian eyes, you really need to step of that style, it looks pretty weird. Try using examples for that 2.
But, despite all my tips, i think you did a really good job, and i hope you learn something from what i said.