I thought you wanted to remove a specific url and not all urls of a specific domain.
You thought correct. I want to prevent certain specific URLs from being predicted when I type something in the address bar. The problem is that when I delete that specific URL from my history, it's still predicted when I type. When i uncheck the option to use opera's prediction service in the settings, it still predicts the URLs I've visited, and continues to predict new URLs (but only after I've visited them once). So far, the only way I've found to delete the saved addresses is to clear all browsing history. After doing that, the prediction service continues to save and predict all the URLs I type in the address bar.
The prediction service is supposed to save me time and effort. Currently, when I want to visit Youtube, opera predicts "youtube.com/user/someyoutubechannel/videos", and i have to write the whole "youtube.com" instead of just "y" in order to visit the front page of Youtube. It's annoying.
I think I'll start a new discussion, because my question/problem was a bit vague in this one, and it's starting to get cluttered. Thank you for your answers