Dumbledore might also play a role. He has vast knowledge and experience. He could offer some wise advice or even provide a special magical item or spell that is crucial for the unicorn's healing.
In such a fanfiction, perhaps Harry uses his magic skills learned at Hogwarts. He might first find the injured unicorn in the Forbidden Forest. Then, using a spell like 'Episkey' or some advanced healing magic he's discovered. The unicorn could be injured by dark creatures or a trap set by poachers.
Obviously, Harry is one of the main characters. Since it's about him healing the unicorn. The unicorn itself can also be considered a main character as the story revolves around it. There might also be other characters like Hagrid. Hagrid could be the one who tells Harry about the injured unicorn in the first place, or he could assist Harry in some way during the healing process.
In a 'harry heals a unicorn fanfic', perhaps Harry uses his magic skills and knowledge. He might find an injured unicorn in the Forbidden Forest. He could use spells like 'Episkey' or some advanced healing magic he has learned. Then he has to deal with the unicorn's trust issues as they are very shy and skittish creatures.
Well, one plot point could be Harry discovers a unique spell to heal the unicorn. Maybe he has to face some obstacles like dark creatures trying to stop him while he's on his way to heal the unicorn. Another could be that the unicorn has a special connection to Harry, like it can communicate with him telepathically and gives him clues on how to fully heal it.
There could be Firenze, the centaur. Centaurs are known for their wisdom about the forest and its creatures. He might be able to guide Harry to the unicorn and provide some herbal remedies or magical advice for the healing process. Also, Hermione could be involved. She would surely do a lot of research in the library to find the best way to heal the unicorn.
One great Harry Potter Unicorn fanfiction is 'The Unicorn's Secret in Hogwarts'. It weaves a tale of a young wizard who discovers a hidden unicorn herd in the Forbidden Forest. The story is filled with magic and adventure as the wizard tries to protect the unicorns from dark forces.
Perhaps a story about an adult wizard who was cursed and turned into a unicorn animagus against his will. He then has to navigate the wizarding world in this new form, facing prejudice from some who don't understand his condition. Along the way, he meets Harry Potter and his friends, who help him find a way to break the curse.
In some fanfictions, Snape might use his advanced knowledge of potions to create a special concoction to heal Harry. He could draw on his skills in Herbology as well to find rare ingredients for the potion.
Well, in some fanfictions, Harry might use his advanced magic skills. He could use a combination of powerful healing spells he learned from Hogwarts or perhaps some ancient magic that he discovers. Maybe he has to face some challenges or overcome certain dark forces that were causing the Longbottoms' problems in the first place.