Collocations for complain - verb

bitterly
She complained bitterly about the lack of help she received.

loudly
constantly, frequently, repeatedly
openly, publicly
privately

cannot
can hardly
It was entirely my own idea, so I can hardly complain.

have cause to, have reason to, have a right to
He really has no right to complain.

begin to, start to

about
All the guests complained about the noise.

at
She complained at the unfairness of it all.

to
I'm going to complain to the authorities about this!

of
45 officers complained of harassment.

Complain is used with these nouns as the subject:
critic, employee, neighbour