He might lose control of his abilities. For example, if his power is related to water, he could cause unexpected floods that harm innocent people or damage the surrounding environment.
It could be that Kronos believes Percy has some hidden potential that, when combined with his powers, would lead to a situation beneficial for Kronos. For example, Percy's strong connection to the sea could be used in a way that disrupts Poseidon's domain and the balance among the gods. Kronos, being the Titan of time and a master of long - term planning, might foresee a complex chain of events that would unfold if Percy had his powers.
One possibility is that Percy trains his powers with the help of his friends. They could create special scenarios or obstacles for him to overcome, which in turn helps him to develop his powers further. His powers could also start to evolve in unexpected ways during this training process.
Maybe there are some dark forces at work. They sense Percy's growing power and want to stop him before he becomes too strong. These could be ancient evils that have been awakened by Percy's power development. They could send minions or create illusions to make Percy's training difficult.
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.
Percy's powers as Aphrodite's son would be very distinct from his Poseidon - given powers. He could possess the power of persuasion in matters of the heart. For example, he could convince two feuding parties to make peace by appealing to their love for something or someone. He might also have the power to make love last longer or end more gracefully. His powers would not be about brute force but rather about the subtler forces of human emotion and attraction.
His water - related powers could take on a more primal and destructive form. Since Titans are associated with great power, his control over water might become more like the force of a tsunami rather than just simple manipulation.
Well, he could have water - based mutant powers. Since Percy already has a strong connection to water in his original story, as a mutant, he might be able to control water on a molecular level. He could create water out of thin air or turn water into ice instantly for offensive or defensive purposes.
He might have more water - based powers related to the ocean's depths. Since Amphitrite is a sea goddess, Percy could have an even greater control over the ocean currents and the creatures that live in the very deep parts of the sea. He could also have the ability to communicate with different sea species that are more closely associated with Amphitrite's domain.
Percy could have the power to manipulate the coldness that is often associated with the Underworld. He could freeze his opponents or create ice - like structures out of the cold energy. This would be different from his water - based powers in the normal story. Also, he may have a stronger connection to the gems and precious metals that are found in the Underworld, being able to sense them and even use them in some way for his benefit.