I thought a girl was hot. I said as much in a "private boy's conversation", but one of them told her and as a result she stopped talking to me.
Fast-forward one year, she asks me out. I didn't think she was hot shit anymore, but I had never had a relationship or kissed someone so I agreed.
We went on a date the next day. It was even lover's day. We started kissing, and I thought it was pretty boring. Plus it was getting late.
So I dumped her right there. Let's say she wasn't very happy about it.
Also when I was 5 years old I bullied an immigrant kid for some time because another kid told me it was fun. But then someone else told me that it wasn't okay and I stopped.