So I'm a New Zealander who lives in Australia: I'm incredibly biased; but the best "hits" that are an absolute spectacle to watch in Rugby Union for me are the perfectly executed tackles, with zero head contact between the players and usually the ball carrier doesn't hit their head on the turf -- now Union still has a lot of the same risks and damage done to players so it's not perfect, but I find the difference between what's considered a "great hit" between the two kind of interesting.

Also, the biggest tackles I experienced playing first-grade union for the Gold Coast dolphins (before I stopped to become a referee) didn't hurt! A perfectly executed powerful tackle stops you in your tracks, looks amazingly impressive, but was reasonably safe.

You're much more likely to get a head injury from either an illegal tackle (that'd result in a red card, removal from the game and a "trial" of sorts before a tribunal) or from being at the bottom of a ruck and being stepped/stomped on