I don't know if I could pick just one red pill moment. It's more like a long series of small cuts that end up scarring, until I finally say "enough with that shit!"
Red pills?
How about the psychological scam that is online dating. It was constantly marketed as one of those helpful tools designed to make life easier. Just like training wheels on a bicycle! So attractive! Much sexy!
Advice from women about life and relationships. Sometimes it can be hard to avoid if the advice-givers are family members, but it seems that even the most well-meaning, sincere advice from your own mother tends to be toxic and subtly designed to destroy your life if you follow it. Maybe your mum spoke a lot of wisdom, but mine always taught me to be a super-nice pushover to the opposite sex. At least she never pushed marriage too strongly.
Family members calling me a misogynist and a woman-hater for daring to question some mainstream feminist views. A few (former) friends were shocked because up until then I'd always seemed like such a nice person. It repulses me that women can be so vile with their shaming and ostracism tactics, when I had done nothing wrong. And it's a recurring theme that women will reject empirical facts if they go against the group's dogma.
In addition, I get pissed at all the past rejections, friend-zoning, and general weirdness of the relationship and dating game. I've kind-of gone "monk mode" out of a sense of self-respect and self-preservation. I don't consider myself TFL/incel, but there's just too much bullshit with unnecessary interactions with the opposite sex.