He might become more confident. As a lord, he has a certain status and power, which could boost his self - esteem.
Well, perhaps one interesting development could be Harry exploring the new powers and responsibilities that come with being a lord. He might use his new status to reform the wizarding world in ways he couldn't before as just a student.
He might become more responsible. As a lord, he has to think about the greater good of his domain. So he may be less impulsive and more calculated in his actions.
He might become more sneaky and calculating. Since he's a thief now, he would have to be good at hiding his actions and planning his 'heists'. His moral compass might also shift a bit as stealing isn't exactly an ethical behavior in the normal wizarding world.
Well, in 'Dark Lord Harry Potter fanfic', the most obvious change is Harry's alignment. Instead of being the hero, he becomes the villain or at least an anti - hero. This completely flips the moral compass of the story.
He becomes more authoritative. Harry, who was once just a student and a hero, now has to make decisions for an entire kingdom. So he has to be more assertive and confident in his actions.
Harry's character could change in that he becomes more of a leader. With the special abilities and heritage from Hecate, he may find himself in situations where he has to take charge. He might also develop a deeper sense of responsibility, not just for his friends but for the wizarding world as a whole. He realizes he has a different role to play now that he is the son of a goddess. Also, he could become more attuned to the more mysterious and darker aspects of magic, which might make him seem a bit more brooding at times.
The fanfiction makes Harry a much more complex character. He's no longer just the good - hearted boy we know. As the new Dark Lord, he might have internal struggles. Maybe part of him still remembers his old values, but the dark power within him is overpowering those. This makes him a more morally ambiguous character, rather than the straightforward hero we're used to. For instance, he could be conflicted when it comes to harming his old friends, but still be driven by the new - found dark desires.
In fanfic, 'Bloodlust' can make Harry more aggressive. He may be quicker to attack and less likely to consider peaceful solutions.
He becomes more assertive. Instead of waiting for others to tell him what to do, he takes the initiative. For instance, he would be more likely to confront the Ministry of Magic directly about their wrongdoings.
The perception of Harry would be turned upside down. In the original series, he is the symbol of good and the one who defeats Voldemort. But in this fanfiction, he is the one causing harm, which makes readers question everything they thought they knew about his character. His motives, actions, and relationships would all be seen in a new and disturbing light.