Ok, first off, your lines are too thick and there's no variation between those making up the pokemon and the background. There should be a difference so one doesn't bleed into the other, usually with the closer image(in this case the character) being thicker lines than what's further behind it(the background).
There's also no line variation in the character itself which would be nice but just making them thinner and smoother I think would help best here. I'm assuming you didn't do this in MS Paint because you've got colouring bleeding and a proper airbrush in there. So you should be able to do line variations easily enough.
You've got shading and highlights here but your colouring is messy with the lines not even filled in properlly in some spots and colouring over the lines in others. Try and zoom in on the image when you're near the end to erase the colours outside the lines and to fill in what's missing.
Hope this helps.
Happy hunting!
~Pika!