My least wanted Smash fighter is Klonoa.
This isn't some grudge against Klonoa, I think he's alright, a solid C-tier platformer mascot, but there's one big problem with the dream traveller...
His main, most iconic ability is inflating enemies using a bullet from his ring, picking them up, carrying them around, and throwing them - this alone isn't a big deal, cargo works for DK and giving each fighter an inflated form wouldn't be much harder than Kirby hats I imagine - but Klonoa usually throws the enemies either straight forwards or straight downwards. Imagine if a fast lightweight had a projectile that activated DK's cargo throw and could go straight into Byleth's up B command grab, would you want that?
I do understand Klonoa has other powers, but the Wind Bullet is his signature ability that most of the combat and platforming in his games is based around. Klonoa without the Wind Bullet would be equivalent to Crash without the spin or Inkling without the Splattershot, and as Smash focuses more and more on game accuracy as time passes the more likely it becomes that should he get in Klonoa would be a wretched pain to deal with.
I don't know if you meant for this post to sound like they're objectively disappointing, but yeah, they both have way more supporters than detractors.