Well, you don't have your shades right on the hair.
If you wanted it to look shaded, you would get a smidge lighter color than black. And follow the colors that they use.
EX:
Look at how different colored the shades look when you zoom in. Almost copy the shade, just a different color.
Get it?
And there are some stray marks.
Make sure that it is even, so your hair style looks complete!