Percy would be completely devastated. He might go into a state of shock at first, unable to believe that Annabeth is really gone. Then he could become filled with rage, vowing to take revenge on whoever or whatever was responsible for her death.
He would likely withdraw from his friends and the demigod community. Percy has always been closely tied to Annabeth, and her death would make him feel like a part of himself is missing. He might start taking dangerous and reckless actions, not caring about his own safety as he is consumed by his grief.
Percy could also become determined to change the world in Annabeth's memory. He might work towards making the demigod world a safer place, or try to find a way to bring her back, even if it means defying the gods or going on a near - impossible quest.
On the other hand, she could try to honor Percy's sacrifice. Annabeth might focus on the reasons why Percy died for her and strive to fulfill any tasks or goals that he might have hoped she would achieve. She would carry on his legacy in a positive way, even though she is heartbroken.
He could also become withdrawn and depressed. Percy and Annabeth have a very strong bond, and her death would leave a huge void in his life. He might isolate himself from his friends and family, lost in his grief and memories of her.
Annabeth could also be angry, not at Percy but at the situation or the forces that led to his death. She might vow revenge and start on a journey to find out who or what was responsible for Percy's sacrifice and make them pay. This could lead her into a whole new set of adventures and challenges as she tries to come to terms with her loss.
Percy would feel a deep sense of guilt as well. He might think that he should have been there to protect her. So, he would be determined not only to free her but also to make sure whoever is responsible pays for what they've done. He would use his powers over water to his advantage, like creating distractions or using water to weaken the enemy's defenses while he tries to reach Annabeth.
Well, if Annabeth dies in a fanfic, it would be a really tragic turn. Percy would be completely devastated. He's been through so much with her, and she's not just his girlfriend but also his partner in all their adventures. Their relationship has been a central part of the Percy Jackson series, so her death would change the whole dynamic. Fans would be heartbroken too, as Annabeth is a very popular character. It could lead to Percy going on a dark path, seeking revenge or just shutting down completely.
Well, it would probably shatter Annabeth. Percy is her closest friend and love. His death would leave a huge void in her life. She might become more withdrawn, consumed by grief. She could also become more determined to carry on Percy's legacy in the fight against the forces they were up against.
It might also be related to some sort of enemy or threat that specifically targets Percy and his relationship with Annabeth. The enemy could be so powerful that Percy realizes the only way to stop it from harming Annabeth is to sacrifice himself, like if the enemy feeds on his life force or his connection to Annabeth, and he chooses to end it by sacrificing his own life.
Some fans might be intrigued. They could see it as an interesting exploration of 'what if' scenarios, even if it goes against the grain of the original story. However, a large number of die - hard fans would probably be quite upset as it goes against the strong bond that was built up between the two characters throughout the books.
Annabeth would be devastated. She and Percy have a deep connection. She might go into a state of shock at first, then be filled with a fierce determination to find out who was responsible and make them pay. She would probably also be racked with guilt, thinking she could have done something to prevent it.
Well, that could lead to a major shift in the story. Percy might be heartbroken and struggle to cope without her.