скаржитися

(комусь — на когось) to complain (to — of), to make complaints (against); to grumble (about, at, over); to be displeased (with)

скаржитися на когось через суд — to sue (to prosecute) a person by law, to lodge a complaint with the magistrate against a person

скаржитися на головні болі — to complain of headaches

на що ви скаржитеся? — what is your grievance?, what do you complain of?