Welcome to Justanswer.com, my name is Dustin.I'm sorry to hear about the issue you are having, I will do my best to help you resolve it.
I definitely sympathize with what you are going through.. Ive had more then my fair share of trolling / hacking lately.. But more importantly, I can help you put an end to this but considering the level of access they have to have to your system to change the URL results locally on your computer, its not going to be simple or easy.
And I want to emphasize the hacking part. As unless you are intentionally googling for this person, theres only one reason they would always appear at the top of your Google search results... Theyve modified some core files, root certificates, DNS servers and several other related files and processes on your system.
But before I go into repairing / denying this person access to your system, can you clarify.
Is it any googles search you do that their result always shows at the top of the screen?
Or almost any?