Ridley

Note: I know the this guy doesn't appear in any sonic game, but I though you should know the bosses from Super Smash Bros. Brawl since Sonic is appearing as a playable character. I don't have very much info on this boss, so I'll put in what I can and put more in later. You can battle this boss as anyone in Boss Mode of the game (You must unlock it first though)
1P's Character: Pikachu or Samus (you choose[you'll play as both if no 2P])
2P's Character: Samus or Pikachu (the opposite of the character you've chosen)
Video of Battle: Click Here to see. (Note: I found this video, but I did not make it.)