LINK
Magic Number is 127%
Initial Thoughts: Link is a solid character, good range, strong out of shield game, potential grab kill combos, decent projectiles, and a little harder to KO off the top.
He is a good weight for getting comboed, he has low mobility, most of his stronger knock back moves are either slow starting and decent recovery or quick and laggy.
Depending on the play style of the Link, he will play a solid ground game with strong jab mix ups, retreating projectile spam for setups, or an aggressive SHFFL game coupled with some offensive projectile mix ups mostly involving bombs.
If you can get around his projectiles one way or another, then you're probably in good shape. If you cannot, then you need to find away, because behind his projectile game is a solid keep out SHFFL game that you need to focus on.
OFFENSE: Shadow balls to cancel boomerangs, Fully charged shadow balls to call boomerang attempts and just punish him. If you catch him as he's landing or not crouch canceling, you can have your way with him with down tilt combos > DJC up airs > forward air > up air or keep messing with him with down tilts > DJC up air > neutral air and link those to either bait an attack or set up another down tilt as he lands. You have all kinds of possibilities once you gain momentum since Link is very similar to Sheik, except heavier so he stays in range of you other stuff longer.
When you land grabs, down throw tech chase, down throw > down tilt if he used poor DI. Cross up teleports (especially through boomerang)> neutral air/grabs...
The most difficult Link players will probably be the ones that can really mix up what they're going for. Bomb drop mix ups with neutral air > jabs > grabs, jab + jab > grab/ jab > jab > grab, and retreating forward air spacing can make it really difficult for you to actually get inside. When you do get inside, he may even crouch cancel down smash your down tilt attempts, so you have to be aware of their percentage and know when you can get the clean tilts or grab.
I unfortunately can't think of anything else to say offensively at the moment. If you can actually use offensive strats on Link then you're in control of the game and will probably win because if you're not in your shield then you're either taking too many hits, or the Link has horrible spacing.
DEFENSE: A lot of your offense will probably start from exploiting attacks from Link. Shield grabbing, bomb catching, tilting boomerangs, Short hopping/Teleporting out shield to avoid shield pressure/grabs/high low combos, and baiting attacks in general will be how you score percentage. I can see good Link players shutting you out pretty well, but Mewtwo has enough tools to force mistakes, or in the rare case against high tier characters, just exploit the flaws in his character like his slower grab, his poor knock back on his quick moves, and the lagginess of his stronger moves in both start up and/or end lag.
Final Thoughts: Not horrible, can be tricky though. One of Mewtwo's better match ups if you can get through projectiles and mix ups. I might have more on this later.