His personality might become more refined. As a goddess, Percy could be more composed and less impulsive. He'd have to think more like a divine being, which might make him more calculating in his actions.
He becomes colder. His emotions like empathy and kindness are gone, so he's more likely to act on pure self - interest.
His personality might become more aggressive. The nine - tailed fox's instincts could seep into Naruto, making him more likely to attack without hesitation. He could also become more solitary as the power might be overwhelming and he doesn't want to accidentally harm his friends.
He might become more fierce. As a dragon, he has the physical power to match his temper at times. He could be less patient with those who oppose him.
He might become more aloof. As a goddess, he'd be in a different social strata than before. He'd be more removed from the daily struggles of demigods and mortals, which could make him seem less approachable.
His personality can become more aggressive. Natsu is usually a hot - headed character, but as END, he can be even more so. He might be quicker to anger and less likely to hold back in a fight.
His personality might become more reserved. As a Cullen, he'd have to fit into their more subdued lifestyle. He might lose some of his brashness.
When Percy is made a god in fanfiction, his personality could shift towards being more authoritative. He has to deal with other gods and manage his own domain. So he might become less impulsive as he now has more at stake. His kindness towards mortals could either increase as he has more power to protect them, or decrease as he becomes more involved in godly affairs. His confidence would likely soar, but it could also turn into arrogance if he's not careful.
His personality would likely become more protective. Since Cerberus is a guardian, Percy might feel an intense need to protect those around him more than ever.
His personality might become more aggressive. The demon nature could bring out his primal instincts, making him less patient and more prone to anger.
She might become more assertive. As a dragon, she has more physical power, and this could give her the confidence to be more outspoken. But she would still keep her kind heart. So, instead of being a shy bystander, she could be more proactive in helping others.