Dunno, testing him out right now.
Edit:
Mewtwo's down B (disable). Doesn't connect unless your opponent is looking at you. I did it to Mario and be completely ignored the attack from behind... Then I flipped him around and bam works, hit Mario a character's length away and stunned him for about a second.
He can't really do much out of throw unless your opponent DI predictably.
Up tilt is kinda awesome, if you hit people with the ball part of the tail, they get launched based on where they got hit from, get hit from the inner part of the tail, you get placed right above Mewtwo's head and he can Up Smash KO you.
Edit2: side b is pretty awful, (looks around for Mael before he does his told you so dance)
Neutral B still throws Mewtwo's backward when he is airborne, can be used to recover if used right.
He can combo A to Down A, or jab 1 into down tilt, it is pretty fucking amazing. It works at any percent....
No wait... He can combo jab 1 into another jab 1 or uptilt. I just combo'd Mario at 100% by going Jab, up tilt, Up Smash and Mario died.
Also did jab, jab, up tilt, jab, up tilt, up smash at 0% and it worked, jab, down tilt, and rand aerial works at any percent.
Down air has a huge hit box where it can spike.
Forward air hits like a truck.
Fair, down smash, and up smash seem to be Mewtwo's go to kill moves.
Edit 3
Last one before I leave, Mewtwo's can jab lock people by going Jab->up tilt-> repeat.
Also heard that Lucina and Marth's neutral B has longer range.
Edit 4:
Confirmation- Lucina, Kirby, and Charizard deals more damage with certain attacks. Flare Blitz has higher recoil.
Pac-Man has a faster Grab.
Diddy has a weaker up air and forward smash, Shiek's fair and bair are nerfed.
Sonic and Ness's back throw has less kill power. Ness's up throw was apparently tweaked.
Rumor: Sound Files for victory themes have supposedly been found for Lucas, Roy (Fire Emblem), and Ryu (Street Fighter)
Nothing confirms that the rumor is true though.
Edit 5:
Some of Ganon's attacks do more damage.
ROB has less kill power on his up air.
Kirby has less start up and ending lag on his inhale (Neutral B )
Edit 6:
Samus's missles are faster, her side tilt also has new hitboxes and sweet spots with new properties. Sweet
DK's punch charges faster.
Luma has less health.
Robin's tomes don't disappear right away if they land on a platform. Making them easier to use.
Lylat Cruise has harder to grab Ledges.
Link's spin slash is harder hitting, and luigi's fireballs are weaker.