Does anyone have any issues with Bowser? Bowser is potentially a terrible matchup beacause he has strong and spammable moves with a ton of range. His strength to KO Mewtwo is self-explanatory, but I'd like to note the up-smash's invincibility. Another hazardous factor is rage, and Bowser is the heaviest character in the game. You will need to rely on a gimp to promptly eradicate a stock before it's too late.
Mewtwo has a few advantages, such as a good edge guard ability as usual, fairly strong moves, and his Shadow Balls, no matter what power. will always pierce Bowser's light armor at los percentages. Other than that, Mewtwo has an enormous hurtbox and greatly light weight, and that's the main issue. If I would rate this, it would probably be 40:60.
On the topic of obnoxious matchups, Yoshi is absolute absurdity. He's generally quicker than Mewtwo, a bit annoying to edge guard, and mainly, practically safe with everything, one way or another. Let me mention some of his effective tools:
Yoshi's f-air is not only powerful, but also has a chance to meteor smash and even start combos. His jab combo is insanely swift and even hits behind him. The first jab is capable of setting up combos, too. The d-air is overall terribly, especially on Mewtwo, who doesn't wanna take any damage. Yoshi's n-air is annoying since it comes out almost instantly, is strong, covers all around him, can potentially KO, and can interrupt Mewtwo's attacks.
Mewtwo does have advantages here, however. He can genuinely use his Confusion and Disable to stop Yoshi on his tracks. He also has Shadow Balls, but they need to be a bit larger to clip Yoshi's aerials. Mewtwo's up-smash and up-throw feel like the most effective options to snag a stock, since I believe Yoshi boasts an above average weight and floaty. And he has the moves to push Yoshi away.
Overall, this is a tough matchup for Mewtwo, maybe 45:55. I'm open to any corrections, though.