The clash of different universes. Batman is from DC and Thor is from Marvel. Combining them in a fanfiction where Batman lifts Thor's hammer is exciting because it brings together two very different mythologies. Batman is a human with no superpowers (except his great intellect and physical skills) and Thor's hammer is a magical, god - like weapon.
One possibility is that Batman lifting Thor's hammer could create a rift between him and the Justice League. Some members might be jealous or worried about his new - found power. Superman, for example, might be concerned that Batman is getting too powerful. On the other hand, Thor himself could come to Earth to retrieve his hammer and there could be an epic battle or an unexpected alliance between the two.
A story could start with Spider - Man and Thor in a battle against a common enemy. In the heat of the battle, Thor is knocked out and his hammer is lying there. Spider - Man, without thinking much, tries to pick it up to use it against the enemy and to his surprise, he can lift it. This sudden turn of events then sets the stage for the rest of the story.
Yes. The breaking of Thor's hammer in the comics is part of complex and dramatic storylines. It can happen for various reasons related to the plot and character arcs.
He might gain new powers or abilities. Since the hammer is a powerful magical weapon, lifting it could unlock some latent potential within Peter. Maybe he can now control lightning like Thor, or he has enhanced strength and durability.
Fanfiction often takes creative liberties. It could be that there is a cross - over event that changes the nature of Thor's hammer's worthiness test. Maybe a powerful magical entity in the Harry Potter universe meddles with the hammer's magic. Harry Potter has shown great moral fiber throughout his adventures. His ability to love deeply, his sense of justice, and his unwavering determination against evil could be seen as the 'worthiness' factor by the hammer's magic, allowing him to lift it.