Obviously, Harry Potter would be a main character. He is the victim of the Dursleys' abuse and his story would be central to the fanfiction. The Dursleys themselves, Vernon, Petunia and Dudley, would also be main characters as they are the ones being arrested. And there might be some wizarding characters like Dumbledore or members of the Ministry of Magic who get involved in the case.
The main characters would surely include Harry Potter. His experience and his reaction to the Dursleys' arrest are crucial. Then, the Dursleys are key characters too. But also, there could be other characters like Hermione and Ron. They might support Harry during this time, offer him a place to stay or just be there for him emotionally. Additionally, there could be some minor characters from the wizarding world who are in charge of the investigation and arrest, such as Aurors.
Harry Potter is the main character as the whole situation revolves around his abuse at the hands of the Dursleys. The Dursleys are also main characters as they are the perpetrators. However, characters like Hagrid could also play an important role. He might be the one who first discovers what has been going on when he comes to check on Harry. And then there could be some new characters introduced, for example, a kind-hearted social worker from the wizarding world who helps Harry deal with the aftermath of the Dursleys' arrest.
One possible plot could be that Harry Potter finally has the courage to report the Dursleys' abuse to the proper authorities. Wizards from the Ministry of Magic, after getting involved, find evidence of the emotional and physical abuse Harry endured over the years. The Dursleys are then arrested and Harry is placed in a more positive and caring environment within the wizarding world, perhaps with the Weasleys.
If the Dursleys got arrested in fanfiction, Harry's life would change drastically. He would no longer have to endure their abuse. He might be placed in a more positive environment, perhaps with the Weasleys or other friendly wizards. This would also mean that the Dursley - related subplots in the story would end, and new ones could start focusing on Harry's new situation.
In the 'the dursleys abuse harry fanfiction', the abuse can be multi - faceted. Physically, Harry could be pushed around or hit by Vernon. Emotionally, Petunia might constantly compare him unfavorably to Dudley, which is really damaging to Harry's self - esteem. And socially, they might prevent him from having any friends over, making him feel completely alone in the world.
In fanfiction, the Dursleys could get arrested for child abuse. They treated Harry Potter horribly, locking him in a cupboard, underfeeding him, and constantly berating him. Another reason might be for illegal use of magic items. If they got hold of some magical objects through Harry and misused them, that could lead to their arrest.
One consequence could be that Harry becomes withdrawn. He's so used to the abuse that he doesn't trust people easily. He might have nightmares often, reliving the moments of abuse. For instance, if Vernon has hit him before, he could have flashbacks in his sleep.
In addition to Harry and the Dursleys, there could be some Hogwarts professors involved. For example, Professor Dumbledore might play a role. He could be the one who arranges for some sort of exchange or interaction between Hogwarts and the Dursleys. Also, Hermione and Ron could be main characters if they accompany Harry to meet the Dursleys or are involved in the events that bring Hogwarts to the Dursleys' doorstep.
Obviously, Harry Potter is a main character as the story is centered around him as a baby at the Dursleys. Then there are the Dursleys themselves - Vernon, Petunia, and Dudley. Vernon is the strict and often cruel uncle, Petunia is the conflicted aunt who has her own issues related to the wizarding world, and Dudley is the spoiled cousin.
Obviously, Harry Potter is one of the main characters. He is the one who has the power to control the Dursleys. And of course, the Dursleys - Vernon, Petunia and Dudley - are also main characters as they are the ones being controlled by Harry.
Obviously, Teddy is one of the main characters. He is likely to be the one driving the story forward with his actions and reactions.
The main characters could also include the prosecutor in Damian's case. This person would be determined to convict Damian and would present all the evidence against him. On the other hand, there could be a mysterious pokemon trainer who has some inside information about what really happened and comes forward to help Damian. And of course, Damian's pokemon could also play a role, perhaps they are taken away from him after the arrest and their fate is also part of the story.