Well, when this happens, there could be a major upheaval in the magical world. Harry's powers might develop in unexpected ways, and his role in the fight against evil could take a wild turn. Also, his friendships and alliances could be redefined.
It could involve a complex web of emotions and power struggles. Maybe Harry is forced into the situation or has some hidden motives.
Harry might become more bold and aggressive in his approach. Since Grimmjow is known for his brash and fearless nature, Harry could start to take more risks without thinking too much about the consequences. He may also become more interested in physical combat rather than just relying on magic. For example, he might start training his body more like Grimmjow trains his combat skills.
A possible fanfiction plot could involve a prophecy related to Harry and Draco being mates. The dark magic that has seeped into Harry makes him more accepting of this bond faster than Draco. Draco, on the other hand, is conflicted as it goes against everything he has been taught. However, as they interact more, they find that they can complement each other's magic in unique ways, and this draws them closer together in a story of self - discovery and acceptance.
Hermione would surely be one of the main characters interacting with Harry. She might try to bring him back from the dark side, constantly arguing with him about his choices and trying to remind him of their old friendship and the good they used to fight for.
He would probably be more power - hungry. Thanos was constantly seeking power through the Infinity Stones. Naruto, who has always been about protecting his village and friends, could shift his focus more towards personal power gain. This might lead him to isolate himself from his friends as he pursues greater power, just like how Thanos was mostly alone in his quest.
If Naruto was Harry's father in the fanfiction, the story's power dynamics would shift. Naruto is used to dealing with threats on a large scale in his own world. He would bring that experience to the fight against Voldemort. Instead of relying solely on the Order of the Phoenix, Naruto might form his own group of allies, including some ninja - like characters he brings from his world. Also, Harry's understanding of loyalty and friendship would be deeper. Naruto values his friends above all else, and he would instill that in Harry from a young age, which could lead to different decisions in the story.
Harry's character would be more conflicted. On one hand, he has his natural inclination towards good from his original Potter bloodline. But on the other hand, Zeref's upbringing would expose him to darker elements. So he would constantly be at war within himself about what is right and wrong. For example, he might be tempted to use more aggressive or unethical magic to achieve his goals, yet still have that inner voice telling him it's wrong. Also, he would be more secretive, not sharing his thoughts and plans easily with others, as Zeref is often a rather mysterious character himself.
In the Harry Potter fanfiction," Starting from Hogwarts," the protagonist artificially created the third generation of the Dark Lord, Peter Pettigrew. The protagonist himself was the Gray Lord, and Harry Potter did not become the third generation of the Dark Lord. Harry Potter and the Prisoner of Azkaban wasn't enough. Everyone, please click to read the novel!
One interesting plot could be Harry's struggle with his newfound dark powers. He might initially resist the pull of the dark side but gradually find that the power it offers is alluring. For example, he could use the dark magic to protect his friends in ways he couldn't with normal magic, but at the cost of his own moral compass.
The Order of the Phoenix would be likely antagonists. Since Harry has turned to the dark side, they would see him as a threat to the peace and safety of the wizarding world. Dumbledore, if he were still alive in the fanfiction, would also oppose Harry. He would try to use his wisdom and power to bring Harry back to the light. Another antagonist could be Neville Longbottom. Neville, who has always been a symbol of resistance against the dark side, would not stand for Harry becoming a dark lord and would fight against him to protect Hogwarts and the values it stands for.