Sakura's confidence would likely skyrocket. In Naruto, she sometimes struggled with self - doubt. But as an Arrancar, with new and powerful abilities, she would feel more in control. This could also make her a bit more arrogant at times. Also, her sense of loyalty might shift. She was very loyal to Konoha in Naruto, but as an Arrancar, she might find new allegiances within the Bleach universe.
Her confidence would likely grow even more. Sakura already has a strong sense of self - confidence in Naruto, but as Catwoman, she would be in a new and different world where she has to rely on herself even more. She might also develop a bit of a mischievous side, which is characteristic of Catwoman. This would be a new aspect to her personality, as she is usually more serious in Naruto.
Sakura's personality could become more competitive. In the ninja world, male characters are often shown to be more competitive. So, as a boy, she might be eager to prove herself against other male ninjas. She could also develop a more laid - back attitude in some aspects, like not being as self - conscious about her appearance as she was when she was a girl.
She might become more aggressive. Saiyans are known for their fighting spirit and aggression in battle. Since Sakura is a fan, she could start to adopt some of these traits. For example, she may be more willing to take on opponents head - on rather than relying on her more strategic ninja approach all the time.
She might be more secretive. Knowing that her father had a dark past due to the Sharingan's influence, she could be more guarded about her own past and family. For example, she might not be as open with her friends in Konoha as she was originally.
The plot could center around Sakura's transformation into an Arrancar being a result of a powerful experiment gone wrong. As an Arrancar, she could discover new abilities she never had in the Naruto world, like the use of Cero. She would then have to deal with the other Arrancars, some of whom might see her as an intruder. And she would also have to figure out how her medical skills from the Naruto world could be applied in this new, more dangerous setting.
She might become more ruthless. Jashin's ideology often involves sacrifice and extreme measures. So Sakura could lose some of her compassion that she was known for. For example, she might be more willing to harm others in the name of Jashin.
Sakura is determined. In a Lord of the Rings fanfic, this would serve her well. Just like Frodo was determined to destroy the ring, Sakura could be determined to achieve her own goals in Middle - earth, whether it's helping to defeat Sauron or something else.
If Sakura Haruno became a Celestial Spirit in a fanfic, it would be a huge transformation. Her physical appearance would likely be more otherworldly, perhaps with a glow and a more fluid form. Emotionally, she might feel a sense of isolation at first as she is different from her ninja comrades. But she could also find a new sense of purpose. She could explore the celestial world, discover new celestial beings, and bring back knowledge from there to the ninja world. For example, she might learn about a new type of energy that could revolutionize the way ninjas use chakra.
If Naruto becomes a hunter nin in the fanfic, his sense of justice could become more complex. As a hunter nin, he'd be exposed to different shades of right and wrong. He might not be as quick to judge someone as he used to be. Instead of simply seeing enemies as bad guys, he'd start to understand the reasons behind their actions. This could make him more empathetic but also more calculating in his approach to dealing with threats. Also, his normally boisterous nature would likely be toned down to avoid attracting unnecessary attention.
Her blindness could make Sakura Haruno more humble. Before, she was often confident in her abilities which were partly based on her visual skills. Now, she has to start from scratch in some aspects. This would lead to a more internal exploration of herself. She might realize that she has been taking certain things for granted, like the ability to see the beauty of nature or the expressions on her friends' faces. This new - found humility could strengthen her relationships with others as she becomes more open and less prideful.