I don't know if this really qualifies, but around the time I was 10 or so, I was invited to a birthday party. The girl's name in question was named Sylvia, but I fail to recall anything other than she was Argentinian and had an older brother. We had talked from time to time and would sometimes hang out in the cement playground in the back of our apartment building.

The party was your standard children's birthday party. But for some reason she and a group of her friends decided to exclude me from the group. I wasn't allowed to be near them, I wasn't allowed to talk to them or participate in any of their activities. It was cruel of them, and it's something that stands out to me as a testament of a child's cruelty.

I left the party in tears, and I hated her ever since.