Often, in fanfiction, jealousy can play a big role. If Percy has some special ability or is getting more attention, his sister might become jealous and start spreading false rumors about him. This would not only damage his reputation but also hurt him deeply as he realizes his sister is not on his side. Another scenario could be when they have different beliefs or loyalties. His sister might side with an enemy or a group that Percy is against, and in the process, say or do things that wound Percy.
A common scenario could be over inheritance or family heirlooms. If there's something valuable in the family that both Percy and his sister want, she might scheme to get it all for herself, leaving Percy feeling cheated and hurt.
In some fanfictions, Percy's sister might hurt him emotionally by betraying his trust. For example, she could share his secrets with others, making him feel exposed and betrayed.
One possible scenario is that Annabeth might lie to Percy about something really important. For instance, she could lie about her whereabouts when she's actually meeting someone who is not a friend to Percy. When Percy discovers the truth, he would feel betrayed and hurt.
One common scenario is when Percy is forced to go on yet another dangerous quest without much support from the gods. He might be angry and show his hatred at that moment. For instance, if he is sent to retrieve some powerful artifact with very little information and no real backup from the gods.
Often, in fanfiction, you'll see Naruto being overprotective when his sister is about to go on a mission. He'll try to convince her not to go, or if she does, he'll insist on going with her. He might also be overly cautious when she's interacting with new people or in new environments. For example, at a village festival, he'll keep a close eye on her to make sure no one takes advantage of her. And if she gets injured, even slightly, Naruto will go into full - on protective mode and might even overreact a bit.
One common scenario is that Percy spies on the Death Eaters or other dark wizards for the Ministry. His knowledge of wizarding laws and regulations could give him an edge in infiltrating their ranks or gathering information about their activities.
One common scenario could be when Percy gets more praise from the gods. Since the gods' approval is a big deal in the story world, Jason might feel jealous if Percy is constantly being lauded by them.
One scenario could be during a training session at Camp Half - Blood. Maybe he's sparring with a new camper who has an unexpected fighting style and accidentally lands a hard blow on Percy. Another is when he's exploring an old, cursed temple. There could be traps that harm him, like poisoned darts that hit his leg. Or he could be in a fight with a mythical creature that has a special power to cause internal damage, like a basilisk's stare which might make his eyes and head hurt terribly.
One common theme could be family loyalty. Since they are siblings, many fanfictions might explore how they support and protect each other. Another theme could be growing up. They may face different challenges as they get older and fanfictions can show how they deal with those changes together.
One common scenario is when Percy is in danger during a battle with a powerful monster. Poseidon might send some kind of sea - based assistance, like a helpful sea creature to fight alongside Percy or create a protective barrier of water around him. Another could be when other gods or demigods try to harm Percy unjustly, and Poseidon intervenes in a more subtle way, perhaps by influencing the situation to keep Percy safe without directly showing his power.
One common scenario could be during a battle with the villains. For example, when facing the Serpentine, Jay might get caught by their venomous attacks which could hurt him badly. Another situation could be an accident while training with his fellow ninjas. Maybe he misjudges a move and ends up crashing into something hard, like a rock or a wall in the training area.