grievance
/ˈɡɹi.vəns/noun
A problem or unfair treatment that gives someone a reason to complain.
Example sentence
- “The workers listed their grievances in a letter to management.”
In workplaces it is a formal term: to file a grievance is to start an official complaint procedure. 'To air grievances' means to state them openly; 'to nurse a grievance' means to keep resentment alive.