In this kind of fanfiction, perhaps Vernon is driven by jealousy. He sees how much attention Harry gets, even if it's often negative attention within the household. This jealousy festers until he decides to take drastic action. It could also be related to some long - held family secrets or grudges that are finally brought to the surface, leading Vernon to try and kill Harry.
Well, in some fanfictions like this, it might be due to a dark magic curse that controls Harry's mind and makes him do it. However, this is a very dark and non - canon concept.
If Vernon kills Harry Potter in fanfiction, it implies a breakdown of the safety net that was supposed to protect Harry. It also shows how a non - magical person can have a catastrophic impact on the magical world. This could lead to a re - evaluation of the relationship between Muggles and wizards in the fanfiction. It might also inspire other characters to take up the fight against Voldemort in a more vengeful way, as they would be avenging Harry's death.
In some fanfictions, it could be a case of a powerful curse that forces Harry to act against his will. The curse might be placed on him by a powerful dark wizard who wants to create chaos in the wizarding world. Draco is just an unfortunate victim of this curse as Harry, unable to control himself, kills Draco. This then sets off a chain of events where Harry has to deal with the guilt and the consequences of his actions.
One possible plotline could be that Harry is under the influence of a dark spell or dark magic artifact which makes him lose control and kill his relatives. Maybe it's a cursed object that he unknowingly comes into contact with, and it twists his mind, leading to this tragic event.
One possible plotline could be that Harry uses his magic in self - defense and this leads to a whole new set of challenges as he tries to hide it from the wizarding world while dealing with Vernon's continued abuse. Another could be that the Dursleys finally get caught by the wizarding authorities for their mistreatment of Harry, especially Vernon's torture.
In some dark fanfiction scenarios, Vernon might kill Harry Potter out of his extreme hatred and fear of magic. Maybe he discovers Harry's magic in a moment of rage and overreacts, using a weapon or his brute force to end Harry's life. However, this goes completely against the essence of the original series where Vernon was more of a bumbling, non - magical threat.
Well, perhaps in a fanfic, Malfoy could be involved in a plot to destroy Hogwarts and Harry, in a fit of rage and desperation to protect his school and friends, ends up killing Malfoy. Or it could be that Malfoy is working with a new, extremely dangerous dark force, and Harry's attempts to stop him go too far and result in Malfoy's death. There could also be a scenario where Malfoy accidentally gets caught in the crossfire of a battle between Harry and another dark entity, and Harry is blamed for his death.
One possible plotline could be that Darkseid is about to destroy Gotham or Earth in a way that Batman has no other option but to kill him. Maybe all of Batman's usual gadgets and allies are useless, and he has to use a kryptonite - like weapon (if it could affect Darkseid) to take him down.
Often, there are plotlines where Harry uses his newfound knowledge from Hogwarts to outwit Vernon. He could use potions to make Vernon see things differently, or use charms to make his life at the Dursleys' more bearable. Also, some fanfictions might explore how Harry's relationship with the wizarding community as a whole helps him in his struggle against Vernon's hurtful behavior. For example, a kind wizard from the Ministry might step in to protect Harry after hearing about Vernon's actions.
Maybe Vernon is jealous of Harry's magical abilities. He might see Harry as a threat to his 'normal' family image. Also, Vernon has always been a bully at heart and Harry, being an easy target in his house, becomes the victim of his pent - up anger.