Got exposed for venting about my coworker-How would you handle this situation?

I was having a particularly bad day at work and I decided to post a rant/vent about a particular coworker of a subreddit related to my field (biology).

What I said was that I found them annoying, condescending, and "know-it-all" as well as some situations I found myself in with them. I made sure to change certain aspects to keep my anonymity. I admit that I omitted certain details to make them look worse, but at the time I just wanted to feel justified in my emotions towards them.
In all honesty, I felt a bit excluded/ignored in group situations with this person. They would always talk over me and ignore what I had to say but never treated my other coworkers the same way. They would also dodge eye contact with me any time I talked to them. I had a feeling they didn't like me but I was too afraid to bring it up. Still, I admit what I did was childish and I didn't foresee that it would have consequences.

A few days later, I get a DM from someone saying "Hey, do you happen to work at <insert name of my workplace>? This sounds like a coworker I know" Safe to say I had a heart attack. Apparently, I hadn't been vague enough and said coworker just so happened to be in that subreddit!! Im horrible at confrontation and I would never in a million years expect this to happen. How would you guys take this L? Do I respond? How would I confront them at work?