I haven't quite come up with a moveset for Mewtwo without a Mega evolutionary stone, but I've been thinking about the strongest "Megas'" for quite some time. Here's what I came up with.
Mewtwo @ Mewtwonite X
Ability: Steadfast
EVs: 4 HP / 252 Atk / 252 Spe
Adamant Nature
- Drain Punch
- Disable
- Light Screen
- Reflect
Alternatives are Protect for Reflect, and Magic Coat or Calm Mind (in this case it does the same thing as Amnesia), for Light Screen.
Unfortunately, if you come across a Ghost type, or a Pokemon resistant to Physical moves, you will have to switch out. I designed this to take on your average opponent, and for being able to take very little damage and heal, as well as getting STAB bonus, provided you being able to set up the defense boosters without taking irredeemable damage.
Mewtwo @ Mewtwonite Y
Ability: Insomnia
EVs: 4 HP / 252 Def / 252 SpA
Bold Nature
- Psystrike
- Reflect
- Calm Mind
- Miracle Eye
This one is able to handle Dark types, and can deal significant damage with it's STAB attack before your health runs out. IT is also able to win against Psychic types, special-attack-resistant Pokemon because Psystrike is based off of defense in the same way as Psyshock, so it can overpower most of the Psychic types, since they tend to have lower defense comparatively to most other Pokemon. However, it can't heal, a Ferrothorn troller would smoke it, and, even with an active Barrier, it's defense is still only 105 according to this very website.
I have recently joined the Pokemondb forum and hope to become a prominent
Pokèmon enthusiast (I use that word too much) in the Poké-base, as well as the rest of the Pokèmon world!