It is close enough to being Rick as to be recognizable. That is good.
I had seen many cartoon designs given realistic treatment and they always looked uncanny. I think this style is meant to be grotesque. This is a design choice so
There is a need to improve the eyelids though, they should stick to the eyeball. Here they look like they are being peeled off. Though, if you stay more true to the cartoon design, the eye should be bulging out. Like this:
I also think you need to improve the eyebrow structure. It just looks too sharp. I know that this is a cartoon character but the sharp eyebrow doesn’t look organic. Again, staying true® to the cartoon design, the eyebrow should be smooth.
Also, how he holds the gun is wrong. The thumb should be on the opposite side of the handle from the other fingers. That is the proper way to hold anything.
While we are talking about the hands, the joints of the fingers have collapsed making them look bendy and squished, while the hand looked deformed. Correct the form. You apply the bone deformation, then manually edit the mesh; or use a shape key to correct the deformations.
There is also some texture stretching especially between the eyebrow and the upper eyelid.
Other things I change would be the hair. It seems to me that you used a single hair particle system for the hair. Try using several hair particles in individual patches, one system for each spike. That would give you more control of the hair that is needed for this stylized hair style.
That is all I can say for now. Hope you find something useful.