Just to clarify, did you try to block users using the process shown here: https://yt.be/help/bhZv ? If so, they will only be blocked from sharing & commenting on your contents. If this is about something else, let us know.
Thanks for clarifying. Have you tried selecting "Not interested" on the video? You may also want to try removing related searches or the video itself from your history, here's how: https://yt.be/help/cJiM