I never had one particular event really. It always stacked up over time. I used to get kicked in the legs purposefully when I played games during recess, got my bangs yanked back several times because I was told I had a big forehead and they'd list cartoon characters that had that trait, and once got a massive block of ice thrown at the top of my head while outside after school in the winter.
I guess one particular event I could think of is when there was this talent show in the 7th grade. I didn't want to do it but the teacher running it gave me loads of pressure because a lack of others were involved. Eventually, the night came. I was singing this song before entirely messing up and I froze. All there was to do was run off stage. Got last place, not even a pitty placement. My mom was supposed to be in the crowd and she actually lied about ever going. She was waiting in the car and told me I did such an amazing job. She never saw me mess up nor comforted me about the situation. Turns out people recorded it and began singing that same song the next day all day whenever they saw me and it continued for a while until it got old.