Could be a great piece, if it was easier to see the individual elements of it. Maybe try different background colors, or shading. It's hard to see Amy on a pink background, or Megaman on an indigo background. Also, the highlight colors of Shadow and that other guy is medium-yellow, which is too similar to the medium-yellow background. Maybe it would also help to make the backgrounds some simple gradients. There's some unexplained white space behind knuckles. The outlines are strangely translucent, maybe that could be fixed with some filters or opacity settings- though the lines themselves are great, everything's on-model.
(Just a suggestion, feel free to disregard this if you don't agree.)