I'm no fan of violence. But I cannot say this bully did not have it coming.

[DirkGently]

45. That kind of blow is often lethal.

The particular features of this "fight" are relevant

1. The kid dishing out the blow was a large athlete. This was a man-sized kid hitting a kid-sized kid. He probably doesn't fully appreciate what that means yet, but it matters.

2. A blindside attack is not a fight. It's an ambush, and people get vastly more injured when they have no ability to react or position themselves. It is extremely, extremely dangerous to hit someone who is not looking. It's relatively rare for anyone in a fight to take the full, maximum force of a blow. They lean or dodge or block to one degree or another. A blindside shot is like someone punching their fist through a wall.

3. Back of the head / sidewalk below. The back of the head is an illegal target in every kind of combat sport. This is where the skull meets the neck, you can do tremendous damage striking that area of the body. And falling onto a hard surface is how many people severely injured by "one lucky punch" end up being crippled or killed. Dropping full force onto pavement will crack a human skull.

Again, I'm not missing that it looks like a terrible kid was the one who got hurt. But I don't think it's a great idea to cheer kids walking up behind someone and potentially crushing their skulls in because they feel the person is a bully.