Her breasts are too big, makes her look more like a cartoon/caricature than scary
What you have now is kind of a chibi nurse, which is cool if that's what you're aiming for.
That was my main idea, to create cartoon-like sidescroller animation with comic ("Bang!","Aghhh" etc.) effects. I need it not to be very complex so i can animate it without a lot of troubles, but also I wanted it to look good. I'm satisfied with the mood in my test mockup but I know it can be improved a lot.
I think you can benefit from some desaturated colors
I agree, your colors look much better then mine. Your edit is great because it very easy to read, and I really like subtle outlines.
@Reo I had the same idea of putting the red cross on her hat but I decided not to, because I didn't now how it will read in animation. I like those veins or dirt on her legs.
@wolfenoctis @Reo Thank you very much for your edits. I will try to use them to improve my sprite, and I'll post new update.