I agree that the Selvadoradan spiders are nightmarish. Even the little spiders that crawl out into the webs from the Vampires pack are icky. (Arachnophobia, lol. Nice job, devs!)
I also think that the drowning animation is gruesome (thalassophobic as well) because it's really realistic looking and less comedic. But I like that about it.
Even the Strangerville possessed Sims have an eeriness to them that I find exciting. The launch for that pack was epic because players had no idea what to make of the impossible postures and macabre grins. <3
I kind of like to be scared and creeped out by the game. This is one of the reasons I really, really want Sims to feel fear and have phobias. It's so human and relatable.