Masataka's torture and rape at the hands of Katsuragi, and let's not go into Souma's childhood.
Katsuragi himself. Not only is he a disgusting pedophile and rapist he also beats his wife up habitually and is a terrifying Yandere for Souma. And then there's the part where Masataka throws a boiling pot of liquid into his face badly scarring his face and his eyes and Souma humiliates him and leaves him and his abused wife sets him on fire. Even if he deserved it, yikes.
The numerous times Masataka and Souma attempt suicide and how Sakurako successfully manages to commit suicide in chapter 9, slitting her wrists open (apparently with the family's katana) and then drowning herself in a nearby pond.
Let's not forget Sakurako's expertise in Cold-Blooded Torture. Not only s/he is to blame for Terashima's death, but the few we learn about what she did to the unnamed maid who was pregnant with Souma's baby... eeeeeeeep.