Percy's personality would be a far cry from the original. He'd be more secretive, for one. Growing up in the Underworld, he'd learn to keep his cards close to his chest. He'd also be more intimidating. His sense of humor might be darker, and he'd have a different moral compass. Instead of the typical heroic values, he'd have values more in line with the Underworld's survival - of - the - fittest mentality. He might be more distrustful of others and less likely to form quick alliances.
He would probably be more haughty. Hera has a certain air of superiority, and being raised by her might make Percy think he is above others in some ways. He could also be more secretive, as Hera often has her own schemes and Percy might learn to keep things to himself.
He'd probably be more brooding. Growing up with Hades, he'd be exposed to the darker side of the mythological world constantly. So, instead of the somewhat upbeat Percy we know, he might be more withdrawn and moody.
His personality would likely be more subdued. Ebisu is a rather proper and disciplined character, so Naruto would probably be less rambunctious.
His personality would likely be more reserved. Manda is not a very expressive or warm - hearted being, so Naruto might not be as outgoing as in the original story. He'd be more cautious and calculating, having learned from Manda's survival instincts.
Naruto's personality would change a great deal. He'd be less naive. Pein has seen a lot of the dark side of the world, and raising Naruto would expose him to that. So Naruto would be more world - weary. He may also be more ruthless in achieving his goals, as Pein doesn't shy away from extreme measures.
Naruto might be more assertive. Since Kushina was a strong - willed person, Naruto would likely inherit some of that. He would be less likely to be pushed around and more likely to stand up for himself earlier. Also, he might be more family - oriented as he would have grown up with a loving mother figure in Kushina.
If Luffy was raised by Whitebeard in fanfiction, his personality would undergo several changes. He would still be the kind - hearted and adventurous Luffy we know, but with added layers. He would probably be more protective of his crewmates, not just in a fight - or - flight way but in a more paternal way like Whitebeard. His sense of justice might also be influenced by Whitebeard's own moral code. He might be less impulsive when it comes to making decisions that affect the whole crew. Instead of just following his gut instincts all the time, he would consider the well - being and opinions of his crewmates more. Also, his leadership style could be a blend of his natural charm and Whitebeard's strong leadership, making him an even more formidable captain.
Naruto's personality would be a blend of his original self and Zeref's traits. He may still have his determination but it could be a darker kind of determination. His sense of humor would probably be lost as Zeref doesn't seem the type to encourage light - heartedness. Also, he could be more secretive, not as open as he is in the original Naruto series because Zeref often keeps his own council.
His personality would probably be more cold and calculating. Voldemort's influence would make him less empathetic. He might be more ruthless in achieving his goals.
He'd likely be more reserved. Artemis values solitude and purity, so Percy might be less of a joker. He'd be more serious about his duties and tasks.