A group of teenage girls heading into the city hook up with a gang of drug-addled ne'er-do-wells and are brutally murdered. The killers find their way to the home of one of their victim's parents, where both father and mother exact a horrible revenge.
This movie contains 53 potentially triggering events.
I don't know what age a certain male character is, so this might not even qualify. He looks to be the same age as the lead teenage character and is treated like a child by his parent. The parent hits him, humiliates him, and forces him to participate in the two worst acts a human can commit.
Nothing seen anyway but heavily implied, you can see red marks on the high inner thighs of a character when a doctor is looking over them and has a very upset face when seeing their genitalia
There is a part where it seems like a main character has drowned, and there is anpart where someone's face is held under water for a long period of time.