The hardcore, no-socializing trait. Must be added to Sims manually with cheats. This is NOT a CAS trait.
Latest: V2b, released after EA Patch, September 5, 2019
With testingcheats enabled, shift-click on your sim and choose Add Social Pariah Trait (or Remove Social Pariah Trait to remove it if your sim has it).
Note that you can add or remove it at any time, your choice! So if, for example, you only want to avoid being targeted by socials for a few sim hours, for some totally normal and not at all weird or nefarious purpose, you could add it temporarily and then remove it later.
With this mod:
If you're a Vampire, I suggest using plasma packs, or removing Social Pariah when you need to feed.
This was made as a trait to use if you want to play a sim who is a total loner with zero interest in other sims (though you are of course welcome to use it for whatever purpose you can imagine!). You can go to a bar and drink, while everyone pretends like you don't exist, to simulate reality more accurately. You can play that person who feels alone in a crowd; who seemingly walks through life like a ghost. Except not a sim ghost, but an actual ghost who no one knows is there. You could do a strange experiment where you have a household full of sims who have this trait and then you film it happening. You weirdo.