The head shape and size is much better now.  His nose, however, still needs to be much narrower, especially the bridge area.  The ears are a bit small.  The chin cleft (that "W" shape) is still a bit extreme.  That being said, it's coming along nicely, but you need to up the contrast between shades and thus use less colors.  Some variation of the hues of the skin tones would also liven it up a bit.  Sorry if any of this is difficult to understand.
What is your native language, by the way?

The cleft is much improved, but that line on his chin is a little off-center.
The skin still suffers from the same contrast issues (make your light shades lighter, make your dark shades darker).  This will also help you cut down on the amount of colors you're using.  Makes sure the next version has more drastic change, or I can't really give any good critique.

So long as you allow a few shades for anti-aliasing, the anatomy should account for most of the realism.   And the color choices.  Which reminds me, the arms and torso are both a bit short, the head and traps are fine.  You do need to decide on your light source, however.  Which could be tricky if the boxer is in the ring.

The anatomy is much improved, now all you need is more hue shifting and higher contrast : )