I am not sure if the question means characters that were deliberately written to be irritating or badly-written characters that are irritating even though they are not meant to be so I am going with somebody who is a bit of both.
Diederich Heßling is supposed to be a character you dislike but I just really really hated him...I have read a couple of other books where the main-characters were also pretty irritating but none bothered me that much. Probably because most 'got better' over the course of the novel so perhaps books with jerks-MCs who keep being jerks till the last page are simply not for me.
Also: I am sorry for the following non-book related content but I couldn't resist
Last night was the strangest football-night in my life and today I might or might not have spent far too much time watching replays of the goals and reading a gazillion articles about the match (hint: I definitely did)