The Hitman Reborn manga ended with a climactic battle and resolution of the main character's story arcs. But it's a complex ending that's best discovered by reading it yourself.
One possible fanfiction could be where Tsuna and Chrome go on an adventure together to find a special item in the Katekyo Hitman Reborn world. They might face various challenges along the way and their relationship could grow stronger as they rely on each other's skills.
Yes, there are quite a few interesting ones. You can start by looking on fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'Harry is Renato Katekyo Hitman Reborn' and you'll likely find some stories that blend the two universes in creative ways. Some might focus on how Harry's character traits interact with the world of Katekyo Hitman Reborn, creating unique plotlines and character dynamics.
The unique character design of the thief OC. If the writer creates a complex and engaging character with a distinct personality, backstory, and set of skills related to thievery in the 'Hitman Reborn' universe, it can be really interesting.
One interesting fanfiction could be where Tsuna snaps and decides to take full control of the Vongola family in a more assertive way. Maybe he stops being so hesitant and shows his true leadership potential.
There could be a fanfiction where the 'game on' concept is taken to an extreme. All the characters are forced into a real - life - or - death game, and they have to use their skills and powers in ways they never thought of before. This would create intense and thrilling plotlines, with characters like Reborn guiding Tsuna through these dangerous challenges.
One interesting crossover is 'The Hitman in Hogwarts'. It combines the unique assassination skills from 'Hitman Reborn' with the magical world of 'Harry Potter'. The story follows a character similar to Tsuna from 'Hitman Reborn' who finds himself in Hogwarts. He has to deal with the challenges of both worlds, like facing the Death Eaters while also trying to control his newfound magical powers.