I can think of another reason why this character is not so hot. His composition has too many damn colors.
Think about it... All Sonic characters (and really, almost all well-designed video game characters) have a well-defined and pleasing color scheme. Sonic has that classic red, white, and blue thing goin' on, while Eggman turns heads with his glamorous crimson and black. Shadic, on the other hand, looks as if he were plunged into a giant vat of churning neon-colored delirium. Seriously, he's dizzying to look at!
There's more wrong with this fan-character than just hue, as Spirit Dragon aptly pointed out. But when you go back to the drawing board, be sure to settle on a good color scheme. You'll thank me later.