Overall, nice!
This is a nice little plot you got going on here! The fighting was also top notch (It was going pretty dang fast), and I liked the idea of a 2 v 2 fight (I don't think anyone has tried that yet). I think shadow also has a chaos emerald, because he was warping a bit while fighting. I at first thought Sonic's meltdown was dumb,until I realized that he was feeling that way because someone DIED!!!!!!! The only things that kept this from a 10 was that you could have come up with a better finisher for Shadow than an energy ball, and the fighting left just a handful to be desired.