The best is almost always full size candy bars, though everyone’s personal favorites are different.
As for the worst, people might rag on the orange and black peanut butter things, candy corn, or circus peanuts. I personally like them all and I feel most of the hate is memetic.
The real bad candy? Peppermints. Even worse and strange? Peppermint candy canes.
Sure, I like them in December, but seeing those mixed in with other candy is an insult and reminds you of Christmas creep. It’s a breath mint. There might be one freakish kid who likes those hard minty disks of Christmas flavor around Halloween, but really, no one is excited about these restaurant give aways. Even hating on the candy you don’t like is part of the Halloween experience, but peppermint just feels wrong in a trick or treat bag.