When Percy joins Kronos in the fanfiction, it affects the other characters in many ways. Chiron, the centaur mentor, would be deeply disappointed. He had so much hope for Percy. The minor demigods who looked up to Percy would be lost. They might lose faith in the idea of being a hero. The relationships that Percy had built over the years would be shattered. His joining Kronos would also make the enemy stronger, which would put more pressure on the remaining good characters to come up with a plan to stop them both.
Percy's reaction could also be one of self - doubt. He may start to question his own actions and leadership. He might think that he has done something wrong to push Annabeth away. However, his loyalty to his friends and the cause would eventually make him stand up against Kronos and try to bring Annabeth back to the right side.
In many fanfictions, Percy might use his water powers in a unique way. Maybe he combines his control over water with his sword fighting skills. He could create a giant water vortex to disorient Kronos and then strike with Riptide while Kronos is off - balance.
It could also inspire some characters to open up about their own insecurities. If Percy, who seems so tough, can break down, it might give others the courage to share their own fears and doubts.
The hunters of Artemis might be caught in the middle. They respect Artemis but also might see Percy as a valuable ally. So, they could be torn between trying to appease Artemis' jealousy and maintaining a good relationship with Percy. For example, some hunters might distance themselves from Percy to avoid Artemis' wrath.
The story would be very different. The loyalty of the other characters would be tested. For example, Annabeth might be heartbroken and try to bring Percy back to the right side. Also, the gods would be in a much more difficult situation as they face a combined threat of Percy and Kronos.
Well, in this fanfiction, Percy might face a huge moral dilemma. Since Kronos is a villain, Percy joining him could be a really dark turn. Maybe he's been tricked or is trying to stop Kronos from the inside. It could lead to some intense battles within the Titan's ranks as Percy tries to figure out his true loyalties.
If Percy Jackson joins Kronos in fanfiction, it would be a huge deviation from the original story. Percy is a hero who stands for good, and Kronos is a villain. This could lead to a very dark and twisted version of the Percy Jackson universe, with Percy using his powers to aid Kronos in his evil plans, perhaps causing chaos among the gods and other demigods.
His friends would be devastated. They rely on Percy in many ways, and his sudden absence would leave a big void. For instance, Annabeth might feel lost without him, as they have a deep connection. She would probably be very worried and try to find him.
It can limit Percy's growth as a character. If Artemis is always protecting him, he might not get to face challenges on his own and develop fully. Other characters might feel sidelined because Artemis is so focused on Percy. For example, some of Percy's friends who also want to help him might find it hard to get involved if Artemis is constantly stepping in.
It could cause a rift among the characters. Some might think he's being selfish by secluding himself, while others might understand his need for privacy. This difference in opinion can create tension and arguments within the group. Also, if Percy has an important role in the group, his absence could make it difficult for the group to function properly in certain situations.