Our paper recently got a "major revision", with comments from three reviewers. Two of them were actually ok, just answers for a few questions and rephrasing of some parts. The third reviewer showed harsh prejudice about our work and their comments were are all marked with and exclamation mark ("!"). I want to know if at the end two reviewers accept and one does not, what will be the editor's decision, specifically for open access journals?
You can't predict what the result of your paper's peer review process will be. Anything can happen, because it's possible the reviewers will say accept and the editor rejects anyway, or the reviewers will say reject but the editor accepts anyway.
Your job now is to use the reviews to make the paper better.
Carefully read and respond to all the comments. Pay particular attention to what you claim is a harsh reviewer. Set aside your perception of the tone and deal with the substance. When they are right, make the change. When you think they are wrong, explain why you reject that particular suggestion.
Then the editor will do what they decide. That is their decision, not merely a tally of the reviewers' votes.