Mecha Sonic (Guardian of the Stone)

Episode 3
The Mecha Sonic only had a major role in this episode. When he spots Sonic, he immediately attacks him. But Sonic took him out with no problem and took the Stone of Chaos.

Trivia

 * A similar version of him went super form to fight Sonic in the opening of Episode 5, but it is unknown if this is the same one as the one guarding the Stone.