I hurt my pet when I was a kid and I still regret it 35 years later...
I had to get creative with the title because it wanted to kick it as opinion. Apparently they don't like the word dog. When I was around 8 years old I took a broomstick and threw it like a spear at my dog and hit him in the back. He yelped. It didn't break the skin or do any damage but I'm sure it hurt and left a bruise. I knew better and I honestly don't know what possessed me to do that. I immediately felt bad. 35 years give or take later I still feel bad about it and think about it from time to time. As far as something I regret having done this is probably my biggest. In all the time since, I've never done anything like that again. I don't really know what the point of this post is but anyway sorry it's not more exciting.