The abuser could face immediate death. Gods like Hades might be quick to drag the abuser down to the Underworld for punishment.
The abuser might find themselves ostracized by the whole demigod community. Word would spread about what they did, and no one would want to be associated with them. Also, they could be targeted by other protective figures in Percy's life, not just Poseidon. The gods and goddesses who have some connection to Percy or just have a sense of justice would make sure the abuser pays for their actions. They could be cursed to have a series of misfortunes befall them, like always being in the wrong place at the wrong time and facing various dangerous situations.
Well, in many such fanfics, the gods might react with anger. They could seek revenge on the abuser. For example, Zeus might send a bolt of lightning to strike the place where the abuse took place as a sign of his wrath.
The gods might be outraged. They could see Percy as one of their own, especially since he has done so much for them. They might immediately seek to punish the abuser. For example, Zeus could send a bolt of lightning towards the person who abused Percy.
It could lead to a stronger bond among the seven. They would become more united in protecting each other.
One possible plot development is that the gods gather to hold a trial for the abuser. They would bring in witnesses, and Percy would have to testify about what happened to him. This would be a very emotional and intense scene.
It could have a negative impact. It might make some fans uncomfortable or even trigger those who have had similar experiences. It could also change the way people view the characters in a way that may not be in line with the original intended portrayal.
Perhaps there's a power struggle in the story world. Percy might be seen as a threat to certain groups or individuals who then resort to abuse as a means to gain control over him. Another reason could be related to his family background. If his family has some sort of enemies, they might take out their anger on Percy.
Personally, I haven't come across a 'the gods find out percy was sexually abused fanfic'. Fanfiction is a vast world, but this type of topic is rather dark and complex. If it does exist, it should be written in a way that respects the nature of the original work and the well - being of the readers. It would need to handle the issue sensitively, perhaps using it as a means to explore themes of healing and support within the context of the story.
The abuser might face the wrath of the DA. They could be ostracized within the wizarding community. The DA members could use their influence to make sure the abuser is held accountable for their actions.
Percy could become more withdrawn at first. The revelation of his abuse might make him more self - conscious and less trusting.