I think every anime has that one character who is both useless to the plot and / or hopelessly annoying. Which character aggrieves you the most? Who should, like the topic says, outright stop existing, so as to cease blemishing your beloved show?
I know some people like him, but my initially thought is Mr. Satan from Dragonball Z. He's annoying. Some of his antics with Buu are mildly amusing, but beyond that... no. Go away. You are stupid.