无端

The child got a beating for no reason at all.

It is not altogether without reason for me to say so.

He began to complain without cause.

be falsely accused and condemned

be criticized without just cause

create a disturbance for no reason; make trouble out of nothing; wilfully make trouble

make an unprovoked aggression

dismiss sb without good reason

attack sb groundlessly/unprovokedly

slander sb groundlessly

get/become angry/irritated over nothing

gratuitous insult/violence

move in endless circles