Originally Posted by Fat TM13IceBeam
The best way of beating Mewtwo imo is to use scarfers such as Kyogre to quickly kill it with Water Spout before it destroys you. If its running a scarf, that's where all the BS starts since you need loljask/lolScarfDeo-A to kill it now and it has the option of tricking away the scarf to something you don't really want it on(cripple it).
If you are truly that desperate, maybe try running CB Sheddy. Sure, Mewtwo can run Fire Blast, but it wants Ice Beam's coverage and the power offered by Psystrike. I guess Aura Sphere's replaceable though...
The Mewtwo I fight on PO tend to use Psystrike, Ice Beam, and Flamethrower, so Shedinja's probably out of luck.
Kyogre may clash too much with my Sun team, but it may be worth an experiment.