I really dislike how an entire settlement/faction instantly aggro's on the player for killing one of their own even when you do it completely silently and out of sight of other enemies.
This had always annoyed me, but particularly so when I tried to kill Aran after returning from the expedition DLC. I closed the door to the bar, killed the barkeeper and patron without making a sound, then stunned Aran with dirty kick and finished him off with my machete, all of which was completely silent and entirely cut off from the line of sight of other characters.
Yet, when I opened the door to leave, the Praetorian guards outside all instantly aggro'd on me, along with the house merchant and other NPCs who weren't even in the same zone as the crime.
I'm all for challenging games, but this strikes me as rather arbitrary and unfair and makes playing a stealthy assassin pretty much impossible since every NPC seems to have an intrinsic, almost telepathic knowledge of every other character's health and location.