This drawing is a few months old but I would like to add some input. I know for a fact would never be able to do this at my skill of drawing. But now to the actual critique.
I'm horrible at it myself and I know how hard it is. His left hand seems a bit off, his feet as well look like a rather unnatural shape. I see the top of the feet should curve down instead of immediately coming down at such and odd angle and a few more toes on the left foot can be added for a perspective effect as well. His torso also lacks the muscles and navel (which probably just bugs me to be honest)
If you're using a program like SAI or Photoshop, I strongly suggest using the magic wand tool to color in the areas you want so it doesn't go outside of the lines to make it look sloppy. I cannot tell where the light source is coming from. The shading is a bit off but it's decent. Also, the rainbow markings shouldn't have a solid black border like it does. This may also be another peeve of mine... but his pants look a bit odd, they seem to just stick to his body.
Overall this is a pretty decent picture but many things can be improved but of course everybody is still learning.
I'm not trying to be mean or anything, I hope i don't come off as such ;m;