Ridley:
+ Good edgeguarding with fireballs and fair taking people off the side, decent range with normals, very strong smash attacks, decent aerials, can reach through platforms with his tilts
- Big body, combo food, deceivingly light for a big character, kind of a bad recovery even though his up B does travel a good vertical distance, has a somewhat useless down B, people can break out of side B, being hit while charging fireballs damages him, smashes have a lot of endlag
Little Mac:
+ high ground speed, KO Punch kills at 10% on most characters, armor on smashes (that are also pretty fast and really strong), fast tilts with decent priority, can 2 frame recoveries with dash attack, forces players to play the matchup - can't just use fundamentals to beat him, has a counter
- Bottom 3 recovery, can't use side B offstage if hit out of it once, dies from one offstage interaction, up B goes nowhere, bad range on many normals, gets camped out hard by every zoner or anyone with a good projectile in general, zero aerial game, KO punch can be knocked out of him super easily, neutral B (charge, not KO punch) is basically useless in a 1v1 environment unless you get a shield break - even then it's arguable if you should just charge an Fsmash or not, can't really edgeguard beyond trying to ledge trap - which is something he can't do that well anyway
Mewtwo (probably the one I know the least about tbh):
+ Decent damage, strong throws, decent combo starters with tilts, good neutral airdodge, decent range with tail attacks, nair is a good 'get off me' tool
o Teleport recovery, can be both good and bad at times, has a reflector
- Big body, tail is a hurtbox, extremely light for a big character, smashes have a lot of endlag, Disable is fairly useless in a 1v1 or even 2v2 environment, Shadow Ball use kind of linear and slow - fairly easy to dodge it
All in all just characters that have ok strengths, but also have a lot of abusable flaws. I probably missed some stuff but I literally never use these characters, I only fight against them here and there. And lose to them from time to time, mostly because I tend to forget how to play the matchup due to scarcity.
But why does it matter anyway? Play who you enjoy using and stop being adamant that some of these characters are better than others say they are with very little to back it up. If you think they're better than that, go out and prove it.