[Fulsrush]

Off the top of my head, both Unknown Armies and Delta Green both feature child abuse as character notes, plot ideas or adventures. An Unknown Armies adventure had a boxout explaining that the horrific things being perpetrated by one NPC against another (I can't remember the details) might seem extreme, but the author relates an anecdote about a case a social worker friend worked on, in which a ten-year-old girl was repeatedly raped by her father and uncle , both at the same time, as an example of how the adventure's horror wasn't actually that far away from reality.

In the Call of Cthulhu campaign, The Masks of Nyarlathotep, it's possible for PCs to get raped by members of Azathoth's court.

Delta Green: Countdown has NPCs who are paedophiles running a children's home, as well as rituals that involve the mutilation of the caster's own genitalia.

Horror isn't just about gribbly monsters that go RAAARRRRR!!! and bite your fingers off. It's about people as well. (In my opinion, fucked up people are scarier than monsters, because they're us.)

People can be fucking depraved. Worse than anything you've ever seen in a film or even in a book.