Woke up early this morning and played Mewtwo for about 2 1/2 hours before I had to go.
After testing his moveset, I deduce that his Forward air is one of his best kill moves, as well as helping create good offstage pressure. His smash attacks, thought slow, are extremely powerful. His up smash, however, seems to be the fastest, with the smallest kill potential compared to down smash or side smash. (I could be wrong.)
Combos I've found:
Specials:
Side B: I've found that you can side b into down smash pretty effectively, supposing your opponent doesn't tech, Nair, or jump away. you can also combo it into a down tilt. My tilt game is horrible as my main is Duck Hunt, so I'll have to work more on that. If your opponent rolls away, you can throw a fully charged shadow ball to throw them off or create stage pressure. I haven't tried connecting it to a jab, but I can see that working.
Down B: This move is pretty explanatory. You stun your opponent for a length of time depending on their damage, then smash attack. Nothing fancy there.
Neutral B: Shadow ball. Nothing too fancy. Can help with stage recovery and can lead into a spacing tool if used in the air right before you land.
Aerials:
I haven't landed a lot of aerial combos, but the ones I did were pretty satisfying. After a few throws (Which I'll cover later) I managed to short hop Fair, Jump Fair, the Fair again. I've managed to do this a few times, but it's not reliable. Think of it like Ness' little wombo combo. It racks up a nice 45-50 damage if you land it, but it's not always easy to do.
Nair on the ground can set you up for tilt attacks or smash attacks if your opponent sucks.
Dair spikes. Typical up in the air juggle.
Uair gets a little tricky. If you can manage to start a good aerial combo, you can get a good 2 or 3 Uairs in. Jump, Uair, Jump Uair, Uair.
Bair, I've found, doesn't combo well. At lower percentages, you can Bair twice, but other than that, it seems to be more of a semi-ineffective spacing tool.
Grabs:
Down throw: At lower percentages, if your opponent didn't tech, you can start a shorthop Fair aerial, which can combo into the Fair combo i mentioned above. If your opponent air dodges, You can punish with a forward smash. However, I've found that at medium percentages, if they DI, they'll get out of your range. Try a shadow ball, perhaps.
Backward: Haven't found much combo potential here. Can combo into some small aerial moves at lower percentages, but your opponent usually has enough time to recover, making it ineffective. Better for throwing offstage for kills.
Forward: Pretty much the same as backward. Good for damage, but not a lot of combo potential.
Up: A good killing move, but not a lot of combo potential. At lower percentages, you can get a small aerial going, but that's about it. Once again, I'm not an expert, so take this with a grain of salt.
Tilts/neutral:
Up: Much like Mario, can be used a few times straight off the ground before your opponent can react enough to get out. You can follow with a Bair for Fair depending on which direction they go, supposing they haven't jumped out of the way.
Down: This has some fairly good reach. At lower percentages, This move knocks an opponent up in the air, leaving them vulnerable for smash attacks, Side Special, Grabs, or Utilt. At medium percentages, this can set up aerials, and at higher percentages, it's effectually a knockback tool.
left/right: Good knockback. Can lead into a dash attack at lower percentages, but not good combo potential overall.
Neutral A: Standard jab with multihit. I've found that I could jab, then head straight into a down smash before my opponent could react. Going with the multihit can set up some aerials upon knockback at lower percents.
Dash Attack: At lower percents, this move can definitely set Mewtwo up for the aerial combo i mentioned before. It can also lead into your Usmash if your opponent is not careful.
Smash attacks:
We're all assuming these are at lower percents here, folks.
Forward: Can set up for a dash attack or some aerials.
Up: Can lead into the double USmash or some aerial combos with Uair or Nair.
Down: Usually better for knockback, but much like USmash, can lead into dash attacks. Not great combo into aerials.
Anyways, that's just what I've noticed so far. I'm no expert yet, so if anything's wrong or you notice something better, feel free to comment. I look forward to playing him again when i get back home. I will say that he seems to be a terrible matchup against other Mewtwos.