What's the biggest dick move you've ever done to a kid and felt absolute remorse afterwards?

I guess this is the opposite of that other topic.

Story:

I was in 5th grade, and the school day had just ended. My school was on top of this hill, and there was just one street that led to it. Lots of kids were literally oozing out of that street to the adjacent park at the bottom of the hill. A lot of kids were on bikes, skateboards, scooters.

Being in 5th grade, I thought I was tough shit, and that jaywalking was no problem for me. As I walked past the first intersection (at the end of the street), I decided to keep walking instead of crossing to the park.

But about 30 seconds later, I decided to just run across the street. Knowing that there really aren't that many cars around, I bolted.

And smacked right into this little 3th grader on her bike.

We both fell. I landed on the grass, got up, saw the commotion, and ran three blocks to home. No one could pin point me since there were a lot of kids.

A week later I saw the little girl. Who happened to be the sister of one of my good friends. Whose arms happened to be covered in scars and scabs. Who looked at me with fiery eyes.

I walked up to her, and before I could say anything, she said the following words:

"Oh hello, Killer."

TL;DR: Jaywalked(ran?) across a street without looking at oncoming traffic, smacked right into a girl on her bike. A week later, she's full of scabs, scars, etc, and she called me "Killer". Feels bad man.

PS: I saw her many years later on my last year in high school, and she actually became hot. I never brought it up to her again, but I'm pretty sure it was on our minds whenever we saw each other.