Some Critique, Please.

[Vipershark]

It's not about making it light, it's about making it visible.

The shade on the hoodie is so dark that I can't see the outline around it in most places, particularly under the arm. It just looks like a large blob of black and then suddenly there's the arm.
On the pants, for example, there is supposed to be a black line running up the side of the pants, right? On yours, it just looks like a big patch of dark green that extends to the rear of the leg, while on mine the line (and thus the detail) is easily visible. Even if you're not trying to make the detail "pop out" per se, you still don't want big ol' blobs of color.

More colors might be fine in a static piece (even then, your contrast is still way too low for the amount of colors you have) but this isn't intended to be a static piece. It's one part of an animation, and at 60 frames a second you simply can't see the details in colors that dark and that close together when each pose will only be onscreen for 1/60th of a second.

Regarding the high contrast, I think you seem to be mistaking the meaning of contrast.
Contrast isn't how dark your colors get, it's about how much difference there is between your shades. As I said before, low contrast end up in your shades blending together, which makes them redundant. Higher contrast makes your shades more visible, and brings out the detail in your sprite.
This is the example in our Spriting Dictionary.

This is the exact same sprite but with different contrast levels. It's a bit exaggerated, but you get the picture. It's hard to see the darkest shade in the low contrast ball because it's so close to the above shade, while the high contrast ball is clearly defined (even if the contrast on this example is way higher than the amount you'd need on your sprite).

Your "main shadow" is simply so dark that it blends in with the outline, completely eating up all the detail. Spriting is about compromises, and this is one that you have to make.