Hermione would be more ruthless. On the dark side, she might have to do things like use unforgivable curses to prove her loyalty. This would harden her heart and make her less empathetic compared to her old self.
She would become more cynical. Instead of seeing the good in people, she would start suspecting everyone's motives. For example, she would no longer trust her former friends easily.
Her appearance might even change. Fanfiction could depict her as having a darker look, wearing black robes all the time and her face would carry a more serious and menacing expression. But more importantly, her values would be completely flipped. She used to value knowledge for the betterment of the wizarding world, but on the dark side, she would use it to gain power and control over others.
Hermione's character might develop a greater sense of adventure. Usually, she's more into academic things in the original story. But in the fellowship, she would be exposed to different cultures and terrains. This would make her more open - minded and adventurous. She could also learn to be more flexible in her thinking, as the fellowship's situations are often unpredictable.
If Hermione joins the BAU in fanfiction, her character would develop in many ways. Firstly, her knowledge base would expand as she learns about forensic science and modern - day criminal psychology. Her magical knowledge would start to blend in unique ways with her newfound skills. Emotionally, she'd become more resilient. Dealing with the horrors of some of the cases would toughen her up. Socially, she'd learn to communicate in a more direct and less academic way, which would be a big change for her. She might also start to see the world in a more grey - area way rather than the more black - and - white view she had in the wizarding world.
The power balance would be severely disrupted. The Rebellion would lose one of its most important leaders, and the Empire or any other dark side - aligned forces would gain a significant advantage. Her knowledge of the Rebellion's strategies and bases could be used against them.
She would become more cynical. Instead of her usual optimistic self, she would start to see the world in a more negative light. Her trust in others would be severely damaged. For example, she might not believe in the goodness of her friends anymore.
Hermione would likely become more conflicted. Her usual confidence and surety in her beliefs would be shaken. She might become more withdrawn as she struggles with the implications of her new identity. She may also start to show more signs of ruthlessness, a trait associated with Voldemort. For example, she could be less hesitant to use extreme measures to achieve her goals.
Ezra would become more ruthless. His once kind and empathetic nature would be replaced with a cold, calculating demeanor. For example, he might not hesitate to sacrifice innocent lives if it served his purpose. His relationships would also change drastically. His friends would become either obstacles to be removed or pawns to be used.
She loses her moral compass. Normally, Hermione is a very ethical character, but in these fanfictions, she may start to see the dark arts as a viable option without hesitation. This could lead to her making choices that harm others, like casting harmful spells on those who oppose her.
Her relationship with Anakin would be severely strained. Anakin, as a Jedi (at least initially in this scenario), would be horrified to see her turn to the Dark Side. He might try to bring her back, but there would be a great divide between them. Their former master - apprentice bond would be tested, and it could turn into a bitter rivalry as Anakin tries to uphold the Jedi way and Ahsoka becomes more entrenched in the Dark Side.
She might become more patient. Hufflepuff values loyalty and hard work, and Hermione would likely adapt to the patient and steady approach of Hufflepuff students. She may not be as quick - tempered when others don't understand things immediately.
She becomes more ruthless. Instead of the diplomatic and empathetic Leia we know, she starts to use fear and intimidation to get what she wants. For instance, she might not hesitate to sacrifice innocent lives if it means achieving her goals.