Hmm. I've already voted here, but I've just had a good idea. So this does not count as my Second vote, it's just for lulz. JUST FOR LULZ, Mewtwo cultists.
Trainer encountered a wild Sonic!
Mewtwo! I choose you!
Sonic isn't paying attention. . .
Mewtwo used Hypnosis! But it failed! (Look into my eyes, dammit!)
Sonic is loitering around.
Mewtwo used Shadow Ball!
Sonic used 'Pssh. Giant balls of evil doom. Yeah, like I've never seen those before.
It missed! (What the hell kind of move is that?!)
Sonic used: Insult Mewtwo's mother! It's SUPER EFFECTIVE! Mewtwo became enraged!
Metwo used Psy. . .
SONICUSEDHYPERKICKSONICUSEDHYPERKICKSONICUSEDHYPERKICKSONICUSEDHYPERKICKSONICUSEDHYPERKICKSONICUSEDHYPERKICKSONICUSEDHYPERKICK
Mewtwo has fainted. . .
Trainer sent out. . .
Sonic used 'I suggest you keep your balls inside your pockets if you want to keep them at all, kid.'
Trainer has fainted. . .
Basically, you can't fight Sonic. Because by the time you've got him in your sights, he's already won.