If you describe something as ~, you are emphasizing that it is so obviously true or real that nobody can doubt it.
He inspires affection and respect as a man of ~ integrity...
There is an ~ link between job losses and deteriorating services.
= undoubted
? questionable
ADJ emphasis
unquestionably
They have seen the change as unquestionably beneficial to the country...
He is unquestionably a star.
ADV: ADV with cl/group