It wasnt a single event, but a sum of various experiences.
It began when I was in high school and noticed that everyone around me started to get laid but I didn't. So I did what a true outcast would: literally typed "how to get a girlfriend" in google.
That was the start of my journey in PUA. I went to a forum thats probably defunct now. Despite all the stupid cope, I still rate that time as a valuable experience: I learned basic redpill concepts like nice guys finish last, also thanks to all those attempts at escaping inceldom, I know that the normie meme of "dude you didnt try it enough" is false.
College was when I took the next dose. When I was in highschool, it was easy to ignore how other people had a social life and relationship. But after I moved into a dorm that had parties all the time - it was blackpill time. I saw how women would - sometimes literally - jump on Chads cock at the first opportunity. I saw how even average looking normie guys were making out with girls 5 minutes after meeting for the first time in their life. I experienced a shitload of rejections because somehow I still believed that by gymceling and cold approaching enough might get me laid.
The next big dose was when my younger sister became a teenager. She grew up in the same shitty environment as me, descended from the same genebase but her life was VASTLY different than mine, thanks to simply having a vagina. I remember reading a post on r/theredpill titled "sperm is cheap and expendable, eggs are valuable" and that perfectly fit the situation. She was surrounded by thirsty betas who would even buy her stuff without asking. She went through highschool with a big social circle. The years that I spent in isolation were a dreamland for her.
The previous experience overlapped with the time when at the end of college, a lot of couples got married.
That was all of it clicked together.
I saw how other people have their life together and starting families, while I'm a KV and spend my time on websites reading about how to grind on some bitch at a nightclub. My eyes were open, and I couldnt fool myself any longer: it was obvious that even if I put in all my energy and do all the redpill tips&tricks, I still would only get 1% of what a normie gets without any effort, and that even if I somehow got a female, it wouldnt be anywhere near to what a normie who naturally got laid in his teens experienced.
That was when I said "fuck it". But that's another story.