What could be the possible consequence if a professor knows about a student's review? Suppose, a student left a negative comment about a professor in the university's confidential review page. Somehow the professor guesses who the student was.

What can the student do if the professor intentionally gives the student bad grades? 

Can the student file a request for a exam paper review to the dean?

How would the whole situation work out for the student?
This totally depends on country, culture etc. (unfortunately, no country tag is given).

A student can of course always file a request. However, this situation sounds so unlikely (how should the student know that the professor guessed and takes revenge) that, without any more evidence, this request will always certainly be dimissed. (And there are also places where no stuff members cares at all about any requests, even if there was proof given.)