There are a lot of ways to upset or irritate your companions in Baldur's Gate 3, some of which are beyond my comprehension. I swear sometimes Lae'zel gets mad at me just for breathing wrong, and choices I think will satiate everyone often backfire. But what about the most distressing, devastating choices that will really put your party in a stinker of a mood?
Reddit user sudosussudio has you covered when it comes to causing the most emotional turmoil to your team possible. They combed through the game's script—though they do mention it's for 1.0 so some tweaks may have happened in the months since—to find the singular choices that would cause the biggest hit to your companions' approval rating. There are a few spoilers here, so if you're not out of the first act yet perhaps steer clear of min-maxing disappointment until you're further in.
There are a couple of ways to significantly upset Astarion, such as being mean to him about biting the drow in Moonrise Towers or not allowing him to turn you into one of his spawn should he ascend. Both of those will do a hefty 15 points of damage to his approval rating.
It turns out it can get a whole lot worse though, especially when it comes to our favourite golden retriever barbarian Karlach. You can end up docking 20 points off her approval rating just for not including her in your slaughter of Gortash, or by being a total douchebag in your dialogue choices should you break up with her. Perhaps the most heart-breaking of all—and the single choice that knocks the most points off anyone's approval rating—is telling Karlach that sleeping with her was a mistake. You'll lose 100 points from her approval rating for such a comment, which you totally deserve.
Ones that admittedly got a chuckle out of me (I'm sorry!) include this 30-point reduction: "Get the book about the Crown of Karsus and tell Gale he can't look at it," as well as playing as Astarion and repeatedly telling Gale that you're definitely, 100% not a vampire. Despite the fact that he totally knows you are a bloodsucking fiend. Sorry Gale, messing with you is just a little too funny.
Surprisingly, sudosussudio notes, killing a companion while playing with the Dark Urge origin only deducts 10 points from anyone's approval rating, meaning it doesn't even make the list of the worst ways to upset your fellow adventurers. I suppose gaslighting is worse than murder in the world of Faerûn.
The entire list is quite interesting, and it does seem like poor Gale and Karlach get the brunt of the upsetting choices. As a perpetual people-pleaser, I'll be using this as a list of what not to do rather than the opposite, but those of you who like to cause a bit of chaos may find greater use of it than me. Just leave my girl Karlach alone, she's been through enough!