I think your lighting setup needs work.
In the first screenshot there's a very strong light in front of the character. Looking at the shadows the light would be slightly above the character and a little to screen left.
In the second screenshot there is a bright light behind the character and possibly some weak ambient or fill light, which is creating very harsh shadows.
A shader, toon or otherwise, probably won't help if your lights are not set up well.
I suggest spending some time to study photographic lighting.
3 point lighting is a good place to start if you're unfamiliar with the subject.
