I sympathize with this so much. I was a very similar kind of asshole in high school. I didnt know how to, and thus "didnt want to" (hoooo boy yes I did) be normal. In middle school being the weird kid isnt great but it wont ruin you. But when I carried that "weird kid" attitude through 9th grade I burnt bridges with just about everyone who knew me. I felt the same way about "not taking shit," that I was some kind of rebel for being an insufferable, argumentative cunt. On top of that I had no sense of personal space which just added to the grossness.
It wasn't until the middle of 12th grade that I started to mellow out, but by that point very few people would interact with me, and I was more or less a "private friend" (wow im using a lot of "quoted phrases"). I distinctly remember the moment I started genuine introspection. One day we were doing a group activity, a jeopardy style review, and I was being very angry and overdramatic like always. After dealing with enough of my shit, the sweet, quiet girl I had a crush on looked me in the eyes and said "you're really mean and loud, could you please stop." Up to this point it was an unspoken truth that I was almost universally disliked, but no one had ever confronted me about why. At that moment, I realized that just because I knew I was an asshole didn't excuse my behavior, it only made people dislike me more. Such a simple realization took me 18 years. All the self loathing and insecurity that defined my personality, well it didn't go away all at once but I finally acknowledged that I wasn't a hopeless prick and that I could actually change my behavior. Sadly by that point it was too late to salvage any of the relationships I had destroyed, but I when I graduated I went as far away as I could. I went to a university in another country on the other end of the continent, and with the knowledge that nobody here knew anything about me I could be whoever I wanted.
When I'm laying in bed at night I often think about all the people I wish I could apologize to, but that moment is gone. I'm stuck in my hometown again now, the shadow of who I was covering the eyes of anyone I might reach out to. But all I can do is appreciate the person I am now and how far I've come from that pent up ball of self hatred that everyone remembers. I doubt I'll be invited to the reunion, but I take comfort in the chance that I might run into someone and show them for however brief a moment that I've changed. And if that never happens, I'll know and the few who stuck by me will know, and that's more than high school me would have thought I deserved.