How to make a statement which makes sense? Is it "We are sure that hardly anybody/nobody/no one will accept the offer? I understand it as "almost no one".
hardly anybody is the correct version here.
hardly is one of those few words that are used in affirmative sentences but they change the grammar of the sentence in such way that it is considered negative (grammatically speaking only).
you can read more about the grammar usage of hardly here: http://www.ldoceonline.com/dictionary/hardly