how should i apoligies, if not what should i do?

Long-time lurker, butI'lll try to make this a short-ish post. I'm currently in college, and at the start of the year I did something horrible. At the time, I was trying to get over a 5-year crush (I know pretty pathetic), and I had superimposed those feelings on someone who looked similar and approached them for it. I told them after 3- 6 months of friendship and obviously freaked out and blocked me. (They unblocked me a year later, aka this year)

Their friends started calling me a stalker, and then they slowly got more people involved, until they were actively befriending others to isolate me socially. They started to target those in my close friend group, and now I can't even trust them; as they could just be close because they want to feed information to said person they didnt even befriend these people cause they were amazing and cunning individuals; it was just a plan to hurt me.

it wored, i couldIt worked; I couldn't be so anxious I couldn't sleep the whole night), cried almost daily, and genuinely the only thing keeping me sane on this earth is my family. Now it's about to be a new year, and I'm going to apologize; I was always meant to, but the person could not stay in the same area or place as me without evading me. Now they have become more comfortable with my existence, and I hope I can deliver a genuine apology. I don't expect immediate forgiveness or the world and my life to magically turn better, but I can't help but feel this is going to go horribly wrong...

How should I apologise?