Over all I have to say I hate several characters equally.
Bowser Jr.- I love the koopalings and he killed them off with his arrival
"Peach"-I really get tired of saving her all the time, and I'd never pick her as a selectable character, I have put quotes around her name because even though I know her full name is Princess Peach Toadstool, I'll always call her Princess Toadstool
Toad-actually he was one of my favorite characters until they made his voice all gravally
Toadette-beating a dead horse
Petey Pirahna-useless
King Boo-see previous answer
The Baby Bros. I understand that the prequels needed a younger version of the Bros. but as selectable characters I cannot stand them
Mallo-as soon as I can switch to Geno and Bowser I do, Mallow is a wuss and a crybaby and overall very annoying
Shy-Guys-actually I like them, what I don't like is how they suddenly showed up in the mushroom kingdom along with Birdo and a few others that are only supposed to exsist in Sub-Con
ok, my rant is over
PS: I Like daisy because she is from Sarasaland, and that is "cannocal Mario" to me