I will admit, I am not a big fan of yaoi ships but when I saw this... This made me fall in love with Sonadow.
I love how you made Shadow's rings glow giving him that: "I am about to kill you and bury you in a closet" Sort of look. The rings lighting up indeed showed how he is the 'ultimate life'
I really like the l guess could say sparkle on the gun. It makes it look new gun actually
After looking at many posters, fan art, and real 3D images of Shadow, I can see where you got the fang but in my opinion its a big large.
I like how Sonic is sort of cringing/dying, although I don't quite understand how this happened. I mean, Shadow actually kills Sonic in Shadow the Hedgehog in an alternate ending.
I like how you smudged the dirt and blood together to show it got very rough.
That's really all I have to say other then this is a lovely piece of artwork.