COMPLAIN, verb intransitive

1. To utter expressions of grief; to lament.

I will complain in the bitterness of my spirit. Job 7:11.

I complained and my spirit was overwhelmed. Psalms 77:3.

2. To utter expressions of censure or resentment; to murmur; to find fault.

And when the people complained, it displeased the Lord. Numbers 11:1.

3. To utter expressions of uneasiness, or pain. He complains of thirst. He complains of a head-ache.

4. To charge; to accuse of an offense; to present an accusation against a person to a proper officer.

To A B, one of the justices of the peace for the county of S, complains C D.

This verb is regularly followed by of, before the cause of grief or censure; as, to complain of thirst, of ignorance, of vice, of an offender.

5. To represent injuries, particularly in a writ of Audita Querela.

COMPLAIN, verb transitive To lament; to bewail.

They might the grievance inwardly complain

This use of complain is uncommon, and hardly legitimate. The phrase is properly elliptical.