Baldur's Gate 3 lets you go full-tilt evil, as I've been discovering in my Dark Urge honour mode rampage—but there's evil that's coded into the game's narrative, and then there's emergent evil. Well, I say 'evil', but I'm not even sure this counts. Two out of three people involved had it coming in some way, though before I can dig my claws into this messed-up turducken: Major spoilers for Act 3 incoming.
This particularly inventive kill of Gortash comes from Syntactics2411 on the game's subreddit. They've sought out, slain, and pocketed the body of Gortash's mother. Then, they've used it to bludgeon him to death as Karlach, the person who Gortash wronged the most, and in doing so they've created a web of moral implications that makes both my head and my heart hurt.
There are three levels to break down, here. First up, Gortash is a massive bastard—as anyone who has romanced (or even spoken to) Karlach can attest. He's chosen of the god of tyranny. A man who would sell you to Bane for a corn chip. He also doomed Karlach to an entire decade as an infernal war machine in the hells. If anyone deserves to be beaten to death with their own mom, it's him.
Did Gortash's mom deserve this fate? Welcome to the swamp of moral ambiguity, it sucks here. Gortash's parents Dravo and Sally Flymm can be found in Flymm's Cobblers, in Act 3's Baldur's Gate. It's an interaction that's easy to miss, but completely harrowing. I've gone ahead and recorded the conversation for your viewing pleasure:
The abridged version is that Gortash's parents sold him to a warlock to avoid paying debts, which isn't the kind of behaviour that wins you mother of the year award. To avenge his misspent youth, Gortash stuffed a mindflayer parasite in their eyes and is now using his command over the nether brain to trap them in their own bodies. Horrifying!
The third and final layer to this terrible lasagna is Karlach herself doing the deed. If you want to get all Oath of Vengeance about it, both Gortash and Sally kinda had it coming. But I don't know if hurling your enemy's dead mom at them like the world's worst javelin is necessarily Karlach's style. A huge part of her character is that the hells didn't turn her into a cruel murderer, and this does seem a step too far. The Dark Urge might do it on her behalf, but Karlach? I dunno.
So there you have it—the most objectively morally grey thing I've seen in Baldur's Gate 3 to–date. A mother who treated her son like disposable property, killed and then thrown at the monster she created, wielded by someone that monster scarred for life—and, in doing so, proving his assessment of her as violent muscle right. Does anybody win, here? I don't think so.