Perhaps the concept of heroes in the fanfiction goes against the OC's values. For example, if the heroes use violence as a first resort and the OC is a pacifist, that could lead to a dislike. It could also be that the fanfiction portrays the heroes as always being right, and the OC, who may have a different perspective, is constantly marginalized.
Another way is to create a conflict where the OC has to work with the heroes despite hating them. This can lead to some interesting character development for both the OC and the heroes. The OC could gradually learn to see the heroes in a different light, or the heroes could realize that they have been wrong in some ways. You can also add some mystery to the story. Maybe the OC has a secret power that the heroes need, and this forces them to interact. This power could be related to something that the heroes have been searching for, but they didn't expect it to come from someone who hates them.
It could be that the OC creator simply doesn't like the typical tropes or storylines often found in Rias fanfiction. For example, if the fanfictions tend to be very formulaic or over - use certain clichés, the OC might be a symbol of a break from that. Also, perhaps the OC has a specific backstory or purpose that is at odds with the general narrative of Rias fanfiction.
You might want to check out 'The Lone Knight in Highschool DxD'. The OC in this story really dislikes the harem aspect and has some interesting interactions because of it.
Well, you might want to check out 'The Lone Warrior in Highschool DxD'. The OC in this one really dislikes the harem concept and it's got some interesting plot twists.
Well, the OC's hatred often becomes a central conflict. It might lead to situations where the OC tries to expose Elena's secrets to Damon or to the whole vampire community. This can cause a chain of events that changes the course of the story. Also, it could make Damon question his own feelings for both the OC and Elena. He might be forced to choose sides, or try to reconcile the two, which adds more twists to the plot. In some cases, the OC's hatred might even attract the attention of other characters who want to use this conflict for their own gain.
Maybe the OC has a completely different personality or set of values from what is often portrayed in Rias fanfic. It could be that the OC has had bad experiences related to the typical tropes or themes in those fanfics.
One example could be a story where the OC has a past encounter with Elena that makes her dislike her. Maybe Elena unknowingly hurt the OC's family in some way in the fanfic. Another example might be that the OC is a vampire hunter and Elena's vampire nature goes against the OC's beliefs, so she hates her. And in some fanfics, the OC could be in love with Damon and sees Elena as a rival for his affections.
The popularity of 'heroes of olympus oc fanfiction' lies in the fact that it allows fans to be creative. They can create their own characters (OCs) and insert them into the rich world of 'Heroes of Olympus'.