How to revoke my old paper from a fake journal (waset.org)?
I think there is something you can do to help yourself in this situation.

You could contact Google and ask if they would remove this particular search hit from their cache. As a result your paper will not come up when people search your name in Google. Of course your paper will still exist in their server but I think that a major part of the potential damage can be avoided since I would believe that people do not intentionally go the predator publishers website to search anyones articles.

Here are the instructions to contact Google: https://support.google.com/websearch/troubleshooter/3111061?hl=en