Fox and Wolf can get out of hand if you aren't good at chaingrabbing or tech-reading. They trounce your neutral game too hard. Fox: stage dependent meaning 50/50. Wolf is probably 45/55 in his favor, but I can't say I've met a wolf main worth writing home about.
Zero Suit Samus is not fun. She can run away, stun you, juggle you, and kill you. N-Air, F-Smash, and U-Tilt are rough. She can't gimp you though. 45/55 imo but a difficult 45/55.
Pit does really well against himself oddly enough, just pray you don't come across someone better with him mid-tourney. 80/30 Fox's favor lol
Mewtwo is by far Pit's worst MU. I'm not even gonna explain it right now lol, it's not fun at all.