One possible scenario could be that Percy sacrifices himself to save Annabeth from a powerful and deadly monster. Maybe a huge and ancient sea creature that only Percy can hold off long enough for Annabeth to escape, but at the cost of his own life.
In some versions, it could be that Annabeth is in a life - threatening situation due to a curse. Percy, knowing that his life force can break the curse, willingly gives up his life to save her. This might involve some sort of magical exchange where Percy's essence is transferred to save Annabeth from an otherwise inescapable doom.
One scenario could be that they are facing a powerful monster. The monster is about to strike Annabeth, and Percy jumps in front of her at the last moment, taking the fatal blow. Another possibility is that they are in a dangerous situation like a collapsing building or a sinking ship, and Percy uses his powers to ensure Annabeth's escape while he stays behind and perishes.
One possible scenario could be that Percy is overpowered by the various monsters in Tartarus. Maybe the sheer number of foes like the giants or the more terrifying creatures there are too much for him to handle, leading to his death.
Well, one scenario could be that Annabeth is reminiscing about their adventures together. In the fanfiction, she might be thinking about how Percy has saved her life multiple times. For example, during their battles against various monsters. Another could be that she's thinking about their relationship, like how they first met and how their feelings for each other have evolved over time. Maybe she's considering the future of their relationship in the context of the fanfiction world.
One possible scenario could be they sacrifice themselves to save their friends. Maybe they are facing an all - powerful enemy that can only be defeated if they give up their own lives. For example, if there is a dark force threatening to destroy their entire world and the only way to stop it is by using their combined powers in a self - destructive way.
One possible scenario could be that they are simply having a lazy morning in bed, chatting about their next adventure. For example, Percy might be talking about the latest sea monster he heard about, and Annabeth could be making plans on how to defeat it. Another scenario could be that they are recovering from a battle and finding comfort in each other's presence in bed.
One possible reason could be her deep love for Percy. She might see his life as more valuable in the grand scheme of things, perhaps because of a prophecy or a mission that only he can complete. So, she chooses to sacrifice herself to ensure his survival.
Perhaps in the fanfiction, there are other characters who are jealous of Annabeth's intelligence or skills. So they start spreading rumors or making unfair remarks. Percy defends her because he knows her true worth and capabilities. He would stand up and say things like 'You don't know her like I do. She's always been there for all of us.'
One scenario could be that Annabeth accidentally revealed Percy's secret identity to someone he didn't want to know. This could put him in danger and make him furious with her.
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.
In a 'Percy Jackson Dies' fanfic, one possible scenario could be that he sacrifices himself to save his friends during an epic battle against a powerful new enemy. Maybe a horde of monsters that are immune to his usual powers overwhelm him while he's trying to buy time for his friends to escape.