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.
It's possible that the author of the fanfiction wanted to show Percy's growth and development in a more extreme way. So they wrote that Percy had an in - depth understanding of Kronos' weaknesses. He could then use this knowledge to quickly and easily take down Kronos. For example, he might know that a certain spell or attack would be particularly effective against Kronos, and he just exploited that weakness without hesitation.
Some of Kronos' minions, like the monsters he commands, could be antagonists. For instance, the dracaenae. They are always eager to prove themselves to Kronos and might see Percy as competition within Kronos' ranks. They could constantly try to undermine Percy's position and cause trouble for him.
Annabeth is often a popular character. In fanfiction, she might play a crucial role in helping Percy deal with his complex identity as the son of Kronos. Grover could also be popular as he's Percy's loyal friend and could be there to support Percy through his struggles related to his new - found heritage.
The other Titans could be main antagonists. For example, Hyperion who is known for his great strength and his desire for destruction. He might not fully trust Percy and constantly try to undermine him in Kronos' eyes. Another could be Atlas, who is already a major foe in the Percy Jackson series. He might see Percy as a threat to his own plans within Kronos' regime.
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.
Annabeth Chase is likely to be one of the supporters. She is smart and strategic, and she can come up with plans to help Percy. Grover Underwood, Percy's satyr friend, might also be there. He can use his nature - related powers to help in the fight. Maybe some of the other demigods from Camp Half - Blood like Jason Grace or Piper McLean could also show up to support Percy.
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.
One key element could be Percy's use of his water - based powers in a unique way. Maybe he creates a huge tidal wave to disrupt Kronos' forces. Another element might be his alliances. He could team up with his friends from Camp Half - Blood, and they all use their combined skills to outwit Kronos.
Perhaps there are some traitors from the other side. These characters, seeing Kronos' power and potential for victory, switch sides and help him in the war. They might provide valuable information about the enemy's defenses and plans.
Obviously, Percy Jackson is one of the main characters. He is the demigod hero with his own set of powers and a strong sense of justice. And then there's Fem Kronos. She is a female version of the powerful Titan Kronos. Her character might have different motives and ways of operating compared to the male Kronos we know from the original myths. There could also be other characters like Annabeth, Percy's friend and strategic partner, who might play a role in the fanfiction, either helping Percy against Fem Kronos or getting caught in the middle of their conflict.