A great drawing!
Concerning your technique there is not much to say, simply that I really admire you skill. You did an awesome job on the shading and the textures. It looks very realistic and supports the eerie atmosphere in this image very much. Period.
What makes your work so interesting is the extraordinary motive.

What is most eyecatching is the perspective.
By means of the angle you guide the viewers gaze right to the creatures muzzle, giving it a considerable meaning. The facial expression manages to evoke certain feelings. Though it is equine it is archetypical, it has a sense of humanity. I mean, everyone could look at it and see that this is either an expression of disgust or pain and despair (which is supported by the title). Either way, it is understood a negative one. Furthermore the directed shading of the mane implies movement. The creature just yanks its head back.
The first thing to notice is that we have a unicorn here - apparently. Firstly, I thought the tribal-like motive is a nice touch. But upon discovering the fangs I thought you might have added it for a purpose more profound. The unicorn is associated with innocence and purity, while the marking and the fangs add some devilish aspects. To me, it looks as if this creature is torn between good and evil (stereotypical, I know. ). Taking a closer look it seems as if the creature is shedding tears. I can't help but think that the marking does as well look as if it was blood. Thus it seems as if the horn did just protrude from the creatures forehead.

To me this leaves an interesting question. Which side was there first: the good or the evil? Or did one induce the other?

Or perhaps... who knows - in the end, it was just the broccoli...

The somewhat distorted view and crazed wildness of this beast is really awe-inspiring as well as disturbing. The pencilwork and shading are positively flawless. Although, I'm rather confused at the fangs. I like that touch, but I only know of a few who have heard of the rare and elusive 'Vampirecorns' found on deviantART.

I think the marking on its head where the horn is, is the most eye-catching. It's where the viewer focuses on first and then moves down to the flared nostrils and the open mouth that seems to silently utter a harsh and unearthly 'neigh' (or a screech, which ever you want).

Overall, I love the well drawn detail, the dark atmosphere and the beast's unbridled wildness.
Truely Awesome