Two things immediately come to mind—King K. Rool and Banjo.
Something about King K. Rool’s attacks just bother me. I don’t really hate fighting him as much as other characters, but a lot of his attacks are annoying. Is it because I see him as Ultimate’s Little Mac? His down throw is probably the worst of the bunch—nobody should have a down throw that buries people into a Smash attack.
As for Banjo, I don’t really like his specials. His neutral B and down B are spammable and annoying to deal with if you don’t have a reflector of some sorts, and he also has another down throw to bury option, but worst part of all is probably Wonderwing. It can come out anytime, it’s incredibly quick, it’s incredibly strong, it beats out any attack I have, and it’s really hard to punish unless you somehow predict it. Its supposed downside is that it has significant endlag, and unless you happen to be both by the ledge (not to mention the fact that you’d have to avoid getting hit by it), chances are the Banjo will panic sidestep your punish. Then again, the only Banjo experience I have is with a friend of mine.
Also, yeah, I hate Zelda’s neutral B too. It’s really used more as a panic button than as a reflector. Though if you start charging something, the Zelda starts using it as a panic reflector anyway.