If you describe something as unacceptable, you strongly disapprove of it or object to it and feel that it should not be allowed to happen or continue.

Is there such a word as inacceptable?

Unacceptable; not proper to be received.

Is it unacceptable or inacceptable?

As adjectives the difference between inacceptable and unacceptable. is that inacceptable is unacceptable while unacceptable is unsatisfactory; not acceptable.