Your character must do something they know will annoy everyone.
Verbal* tics are the easiest to pull off as a writer but you need to take care not to irritate your readers too much either.
*Non-verbal tics also work, obviously, but they are annoying to write and the eyes of most readers will quickly just pass them without touching.
A few other things:
- littering
- dropping cigarette butts in not quite empty glasses
- putting a pacifier in their mouths each time they think of their baby, months after their wife gave birth.
@Jantar
Think more along the lines of the character having to make a decision that will lead to people being upset, but is something they feel they must do.
All right.
The first thing coming to mind is something that happens quite a bit in real life too:
A grown-up person moving back to the place they came from, to take care of a dying parent who had abused them while they grew up and whom they had succesfully escaped by creating a happy & successful new life with a tight group of chosen family.