A popular one is 'Potter in the DC Universe'. In this, Harry is sent to the DC universe due to a spell gone wrong. He has to adapt to a world without magic in the traditional sense but with super - heroes everywhere. It shows how his wizarding skills can still be useful in this new and different world.
There's 'Magic and Metahumans'. This fanfiction has a great plot where the Death Eaters from Harry Potter somehow end up in Metropolis. Superman has to deal with their dark magic while Harry and his friends try to find a way back to their world. It's full of action and interesting character dynamics.
There's 'Martian Magic: A Harry Potter - DC Crossover'. In this fanfiction, the Martian Manhunter discovers the wizarding world of Harry Potter. It's a great read as it shows how the Martian's unique abilities interact with the magic of Hogwarts. It also has some really cool team - up moments between the characters from both universes.
One common theme is the clash of different power systems. In Harry Potter, there's magic, and in DC, there are super - powers. Fanfictions often explore how these two types of powers interact, whether they complement each other or cause conflict.
There's also 'Harry Potter in the DC Universe'. In this fanfiction, Harry finds himself somehow transported to the DC universe. He has to use his magic skills while also dealing with the superheroes and villains there. It's a really cool concept as it shows how his magic can be both an advantage and a source of confusion in a world full of super - powers.
One idea could be that Harry Potter and his friends are transported to the DC Comics universe. They could team up with the Justice League to fight a common enemy like Voldemort who has somehow gained powers from a DC Comics villain. For example, Voldemort could have made a deal with Darkseid to gain more power in exchange for helping him conquer the wizarding world first. Then, Harry and the likes of Superman, Batman, and Wonder Woman would have to combine their magical and super powers to stop them.
There's a story on AO3 where Batman visits Hogwarts to investigate some strange disappearances. What makes it stand out is how well the author captures Batman's detective skills in the magical setting. He's able to use his gadgets and his wits to figure out that a Slytherin student is using a dark magic spell that's related to a DC Comics - style super - power experiment gone wrong. It's a complex and engaging plot.
It could be really exciting. Maybe Harry Potter characters could visit Gotham City. Harry could use his magic to help Batman fight crime in a way that normal gadgets can't. For example, he could use spells to disarm villains from a distance or create magical barriers to protect civilians.
There's a fanfic where Harry Potter somehow ends up in the DC universe and teams up with Superman. In this story, the lemon part comes in as a slow - burn romantic sub - plot between Harry and Lois Lane. It's an interesting take as it shows how different magical and super - powered characters interact not just in terms of fighting villains but also in the realm of relationships.
I think Darkseid would be the most unexpected. Imagine Harry Potter being raised in Apokolips. He would have to adapt his magic to survive in such a harsh and evil - dominated place. His magic could potentially be a threat to Darkseid's rule, or he could learn some dark magic - like powers from Darkseid's regime, which would completely change his character and the way he uses magic.
Another interesting one is 'When the Bat Meets the Boy - Who - Lived'. In this fanfiction, Batman and Harry Potter cross paths. The story delves into how two very different heroes with their own moral codes and ways of doing things can work together or clash when faced with common threats.
There's also 'Potter's DC Adventure'. In this fanfiction, Harry finds himself in the DC world and gradually forms relationships with different characters. It's a great read if you like to see how the two different fictional universes blend together in the context of a harem story. The author does a good job of maintaining the essence of both the Harry Potter and DC worlds.