That may be complained of.

(intransitive) To express feelings of pain, dissatisfaction, or resentment. / (intransitive) To make a formal accusation or bring a formal charge. / To creak or squeak, as a timber or wheel.

simple past tense and past participle of complain

present participle of complain

The act by which someone complains; a complaint.

(law) The party that brings a civil lawsuit against another; the plaintiff. / (law) An alleged victim in a criminal investigation or trial. / One who makes complaint.

Third-person singular simple present indicative form of complain

plural of complainer

One who complains, or is known for their complaints.

plural of complainant