It seems like every cartoon we ever watched needed a character whose sole purpose was to piss us off, and in the case of these 10, they were very, VERY good at it.
Tiny Toon Adventures - Elmyra Duff
I almost want to cut her some slack because she's a young girl who loves animals and clearly doesn't know any better, but good lord was she annoying for every second of her existence. Not only that, but hurting animals isn't exactly a great way to win any love from the audience.
The Flintstones - The Great Gazoo
You know your show's running out of ideas when you introduce an alien that can warp reality at will and that only one or two of the characters can see. Gazoo's antics were annoying enough, but his pompous voice just made him the worst.
Arthur - D.W. Read
D.W. was basically every bratty sister combined into one character. Tattle-tale? Check. Cries when called out on her BS? Check. Constantly snooping into things that don't concern her? Check. Ugh, she's awful.
Dexter's Laboratory - Dee Dee
It has to be hard to be a six-year-old kid with the mind of a genius, and it's gotta be even worse when your sister is a constant terror. Every time Dexter had a new invention or experiment in the works, you could bet that Didi would show up and ruin it.
Sure, she cared about her brother and was mostly just dumb, but it was hard not to want her to just go away.