One possible plotline could be that Harry discovers some dark family secrets that lead him to embrace the dark side. Maybe he finds out that his connection to Voldemort is more complex than he thought and decides to use that power for his own gain instead of fighting against it.
Perhaps there is a plotline where Harry, as the dark prince, forms unexpected alliances. He might team up with characters who were once his enemies, but now they see a common goal in his new identity, which could lead to some really complex and exciting story developments.
One possible plotline could be that Harry discovers his true heritage as a prince of hell and has to grapple with the dark powers that come with it while still trying to exist in the wizarding world. Another could be that he is in conflict with the forces of good in the wizarding world as they view his newfound identity as a threat. Maybe he has to form new alliances with darker creatures or beings from the underworld.
One plotline could be that Harry is influenced by the Dark Lord's ideology from an early age. Maybe he discovers some 'truths' as he sees them that make him believe the Dark Lord's way is the right one. For example, he might think that the wizarding world's current order is corrupt and only the Dark Lord can fix it.
One interesting plotline could be the exploration of the 'Dark Prince' character's backstory. Maybe they have a complex family history that led them to their dark path. Another could be the unique magical abilities the Dark Prince has that set them apart from other characters in the Harry Potter universe.
One possible plotline could be Harry discovers his latent archmage powers early on and uses them to quickly defeat Voldemort. Another could be that he has to go on a journey to learn how to fully control his archmage abilities while still dealing with the normal Hogwarts stuff like classes and friendships.
One possible plotline could be that Harry discovers his siren abilities during his time at Hogwarts. At first, he's confused and scared by these new powers. He might accidentally use his siren voice to make a teacher or a student do something they don't want to. Then he has to learn to control it with the help of Dumbledore or another magical creature.
The businessman could be trying to revolutionize the wizarding education system from a business perspective. He sees potential in making Hogwarts more efficient and cost - effective. He proposes ideas like installing modern muggle - like technology for administrative purposes or outsourcing some non - magical aspects of the school's operations. This causes a stir among the Hogwarts staff and students. Another plotline could be that he is a muggle - born who made it big in the muggle business world and now wants to use his wealth and influence to improve the status of muggle - borns in the wizarding world. He funds projects and initiatives that aim to bridge the gap between muggles and wizards.
Perhaps in this fanfiction, there could be a new, unexpected hero emerging. Maybe Neville Longbottom finally steps up in a big way. Since Harry is dead, Neville could be the one to find a new way to defeat Voldemort, like discovering a long - lost spell or uniting the houses in a way that has never been done before.
Another plot could involve Harry being tricked into taking the Dark Mark. He might think he's doing something else, like a magical experiment or a ritual to save someone. But it turns out it was a setup by a dark wizard. Harry then has to face the consequences, not only the physical and magical changes brought by the Dark Mark but also the change in how others perceive him, especially his friends who might be shocked and scared.
Another plot could involve a magical tournament that somehow brings Harry Potter and Dark Sakura Matou together. They are forced to compete against each other at first but then realize that there is a greater conspiracy behind the tournament. They then join forces, with Sakura's dark magic and Harry's quick thinking and diverse spellcasting abilities becoming a formidable combination to uncover the truth and defeat the real villains behind the scenes.