In some fanfictions, the relationship might start with fear. For example, if Harry first encounters the tyrant dragon during a dangerous situation, he would be scared. But as he realizes the dragon has a reason for its aggression, like being mistreated by other wizards, he starts to feel sympathy. This could lead to a bond where Harry tries to protect the dragon from those who want to harm it.
In a 'living with dragon' fanfiction, Neville could find a way to use his knowledge of plants to feed the dragon. He might discover certain magical plants that are a dragon's favorite. Ginny would be fearless and would probably be the first to try and train the dragon to do tricks. The Weasley twins would surely come up with some inventions to make living with the dragon more fun or easier. The dragon would also interact with the Hogwarts ghosts. Peeves might play tricks on the dragon, while the Fat Friar would try to keep the peace between them.
They could use magic spells to calm the dragon first. For example, the 'Diffindo' spell might be used to cut ropes that are binding the dragon in an aggressive way, showing the dragon that they mean no harm. Then, they can start communicating with it using Parseltongue if they have that ability, like Harry does. Maybe the dragon has some knowledge about the puzzle and can give hints if it trusts the characters.
Perhaps in the fanfiction, the tyrant dragon is actually a misunderstood creature. It was once a normal dragon but was experimented on by a group of rogue wizards. Harry and his friends, Hermione and Ron, then decide to help the dragon by finding a cure for its 'tyrant' state. They go on a journey through various magical places in search of the ingredients for the antidote.
In many fanfictions, Harry might use his powerful spells like the Stunning Spell or the Killing Curse if the story allows for such dark magic use. He could also use his intelligence to outwit the dragon, perhaps finding a weakness in its armor or behavior pattern and then using a well - timed spell to defeat it.
It could be that the dragon was an egg he found by accident. He, being curious and having a soft spot for magical creatures, took the egg and hatched it, thus becoming the owner of the dragon. In the wizarding world, there are often unclaimed or lost magical items and creatures, and Harry might have just stumbled upon this dragon egg.
Another way is through a shared danger. Suppose there's a new threat in the wizarding world that endangers both Slytherins and Gryffindors. Malfoy and Hermione, along with Harry, have to put aside their differences. In the face of this danger, Malfoy might have a change of heart and begin to respect Hermione. Their relationship could develop from grudging allies to something more like friends. This could be a slow process, with many bumps along the way as they both struggle to let go of their preconceived notions.
Often as very powerful and alluring. Their dragon traits like strength and a bit of mystery make them attractive to other characters. For example, they might be shown as being able to protect their love interest in a very fierce way because of their dragon abilities.
Hermione Granger is also a popular character. In some fanfictions, she uses her vast knowledge to study dragons in a way that no one has before. She could be researching dragon magic or trying to find a way to communicate with them on a deeper level.
Obviously, Harry Potter is one of the main characters. Since it's a fanfiction about him as a dragon or related to dragons, he would be central. And I think Hagrid would also be an important character as he has a great love for magical creatures, especially dragons. He could be the one to help Harry understand his new relationship with dragons.
Often, the main characters can include the well - known Harry Potter characters like Harry himself. He might get involved with dragons in some way, perhaps during one of his adventures outside of Hogwarts. Another common main character could be a new, original character created specifically for the fanfiction. This character could be a dragon trainer or a researcher of magical creatures, with a special interest in dragons.