Virtually every example of a "big hit" in that video ends with the person who got hit showing the fencing response (https://en.wikipedia.org/wiki/Fencing_response). That body pose indicates a pretty severe concussion.

In fact, the most popular video on YouTube about the fencing response has a shocking amount of overlap with the "big hits" video you shared. https://www.youtube.com/watch?v=ZlXjwAlOflA

Frankly, your video was kind of hard to watch. It's basically 3 minutes of people getting their brains rattled in their skulls.

That's true! I didn't think about it because it was a collection of "rare" events - hitting above the shoulders is not a valid tackle. Usually won't get these hits in a game.

But still, obviously it certainly exists, and I'm sure there is a lot of head trauma every year.

I have never seen this video. I always had heard that without the gear that rugby was less brutal than football -- but seriously I don't know. Those hits looked devastating... I could not watch that sport.

That's not rugby, it's Aussie Rules, but those are illegal tackles in both sports. I don't know why the poster chose a video of vicious fouls to make his point about safety.

What % of players are going to get such a tackle once in their careers? How many are going to get five?