On a personal level, Percy might have to deal with the emotional toll of killing Kronos. It could be a very traumatic experience for him, even if Kronos was an enemy. He might have nightmares or second - guess his actions. Also, his relationships with other characters might change. Some might fear his new - found power, while others might be more drawn to him because of his victory.
One possible consequence is that the demigod world would be thrown into disarray. Percy has been a key figure in maintaining some sort of order, and with Kronos in control, that order would be shattered. Another consequence could be that the Gods would be in a real bind. They already had trouble with Kronos before, and now with him in Percy's body, it would be much harder to fight him.
One consequence could be Percy becoming an outcast among his fellow demigods. Since his powers now come from Kronos, they might see him as a threat or a corrupted being.
Well, one possible consequence could be that Percy gains an immense amount of power. Kronos was a very powerful Titan, so Percy might become nearly invincible. He could also face some internal struggles as Kronos' essence might try to influence his mind and actions.
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.
Maybe there are some original characters created by the fanfiction author. These characters could have their own unique abilities and backstories. They might be the ones who tip the scales in Percy's favor, for instance, by having a special power that weakens Kronos just before Percy makes the final blow.
Luke could also be a prominent character. Since he has a complex relationship with Kronos in the original story, in fanfiction he could play a role in either helping or hindering fem Percy's efforts against Kronos. Nico di Angelo is another possibility. His powers over the dead could be useful in a fight against Kronos, and he might team up with fem Percy for that reason.
I'm not sure specifically as there could be many different takes on it. It might involve Kronos, a character from a particular mythology or fictional universe, killing Percy, another character. Maybe it's a dark exploration of power, rivalry, or a twist on the original story where Kronos overcomes Percy in a rather unexpected or brutal way.
A common theme is the power struggle. Kronos is a very powerful being and Percy is constantly fighting against his power, which makes for an exciting dynamic in the fanfiction.
If Kronos were to win in a Percy Jackson fanfiction, it would be a cataclysmic event. Kronos represents the old, chaotic order. His victory would mean the collapse of the current pantheon - based system. The gods' domains would be up for grabs, leading to widespread conflict among the Titans and other powerful beings. Percy and his allies would have failed in their quest to protect the world. The very fabric of the Percy Jackson universe, with its themes of friendship, heroism, and the fight against tyranny, would be shredded. It would be a very different and much darker world than the one we see in the original series.
In fanfiction, Kronos's role is not just limited to being a villain. Sometimes, he can be a catalyst for character development among the demigods. His actions force the heroes to become stronger, both physically and mentally. For instance, his threat might make Percy Jackson more determined to master his powers. Also, Kronos can be used to introduce new plot elements, like a new weapon or a magical item that has the power to stop him.