The Dark Master. We don't get a very good look at him in the film, but a promotional still of him exists (seen on the right) and holy hell, what is that thing doing in a kids' movie?
It ups the Nightmare Fuel when we find out that the Dark Master symbolizes Jess' father played by Robert Patrick, while the father himself isn't that bad of a guy, it does stir up some repressed T-1000 memories.
Even if you know it's coming, Leslie's death is this. Made even worse by the fact that it takes place offscreen. In the books at least Jesse is in denial that she drowned because swimming is one of her hobbies while in the film she reveals she made it up. Mr. Aarons reveals that she swung by herself and the rope snapped on one of the rainiest days of the year when the river was overflowing. The adults don't know exactly what happened, but they think she hit her head on the rocks and got knocked out before she could pull herself to safely. So either she drowned while unconscious if we believe them, or while struggling to get to the banks and succumbing to hypothermia and exhaustion if you go by the Fridge page. Either way, it wasn't a pretty way to go. They also took a few hours to find her body because they're used to the kids being away all the time.
Earlier that day, Jess decides to tell Leslie they are not going to Terabithia because the river's too high and it's dangerous to cross with the current. They were going to have fun doing something else. He feels really guilty on realizing that if she had come to the museum with him, then she wouldn't have died.
The worry that Jess's family feels, so much that they actually wait for him to come home because they fear the worst. Maybelle knows that Jesse is okay because she gave him the phone for Miss Edmunds to talk to him and she knew Jesse was leaving with her, but his parents and other sisters don't (and potentially think Maybelle is in denial when she tries to tell them). They spend the whole day as the cops and ambulance take away Leslie's body but there's no sign of Jesse. It's no wonder his mother hugs him with tearful relief while his dad is oddly sober.
Jess later sobs to his father that he fears that Leslie is in hell because she doesn't believe in the Bible. His dad reassures him, but it's a scary thought. It doesn’t help that the book mentions that Leslie is a straight out atheist.
In the book, the scene where Jess goes to Terabithia alone using a fallen log. Then he hears Maybelle calling for help. Jesse panics on seeing her trapped on the same log, flashing back to how Leslie died. He rushes over and quickly helps her to the safety of the banks, before either of them can fall. Maybelle then reveals that she was scared because Jess had just vanished after milking Miss Bessie and was worried he had just vanished. Jess apologizes for scaring her, realizing how she must have felt. He would have lost his best friend and his little sister.
Janice Avery's home life, which is presumably why she bullies the younger kids, as a way to vent her frustration.
