Off the top of my head I don’t remember how much the book of #Dune talks about the Harkonnen use of gladiatorial combat, but the movie draws a relatively subtle link between their idea of it and bullfighting - the guys in the wide black hats are like picadors, who stab the bull with lances to weaken it. I’ll avoid spoilers on a 60-year-old book or the new movie, but it’s a fun subtle thing.
I’m not really talking about the challenging. That’s just like duels and having stand-ins so the nobles express discontent while killing other people instead of themselves. It’s more how both houses have ways of proving the butch manliness of their leaders in front of the masses - the #Atreides kill bulls, the #Harkonnens kill captives. Even if the other houses have versions of that, there’s a very specific resemblance between Atreides and Harkonnen.