If the oc hates it but still wants to give it a chance, they could try to find a different take on the rias fanfic. Maybe look for ones that are more in line with their own values or interests. For example, if the oc is interested in action, find a rias fanfic that has more action elements rather than just the typical romance. Another thing to do is to try and write their own version of a rias - related story that they would like, incorporating the elements they enjoy and leaving out the ones they don't.
The OC can simply avoid reading any more of that fanfic. There are plenty of other stories out there in different fandoms or even within the 'High School DxD' fandom that might be more to their taste.
One option is to simply avoid reading or engaging with Rias fanfiction. If the OC hates it, there's no need to subject it to that content.
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.
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.
If Ash hates Serena fanfic, perhaps the fanfic community could come up with some guidelines. These guidelines would ensure that the fanfics respect the essence of all the characters, including Ash. They could also encourage creativity in a way that doesn't make any character feel misrepresented or out of place. Additionally, the creators of the fanfic could ask for feedback from the broader Pokemon fan community to see if their work is likely to be acceptable to characters like Ash, based on the general understanding of the characters' personalities and the world they live in.
One option could be to simply avoid showing Karin any Sakura fanfic. Respect her feelings and keep that type of content away from her.
He can simply avoid reading it. Just stay away from any fanfic related to Edward and focus on the original work or other things he likes.
Well, she could simply avoid reading them. There are plenty of other things related to Sonic that she can engage with, like the official games, comics, or animated shows.
One thing that could be done is to keep the fanfics away from him. Don't show him any new fanfics or talk about them in his presence.
The writers could stop writing that type of fanfiction if they respect Ash's 'feelings' (assuming he were a real person with real opinions).