The universe bad trope.
MC is an Orphan? BULLIED. MC sits in class? STUDENTS PUNCH HIM AND REMINDS HIM HE’S A POOR ORPHAN. Mc fights back? TEACHER PUNCHES HIM AND TELLS HIM HE’S AN UGLY POOR ORPHAN. Mc makes a friend? FRIEND BULLIED, FRIEND PUNCHED FRIEND DIES. Mc goes home to orphanage? GETS PUNCHED BY FOSTER PARENTS. Mc pets a cat? CAT MURDERED, CAT PUNCHED BY BULLIES. Mc complains? GET PUNCHED GET STABBED.
You can give your character a sad backstory without every single character being unrealistically cruel and mean all the time.
Fun? Fact: That book inspired the Oklahoma City Bombing.