Well, a Cadmean victory fanfic could be really interesting. It might involve a battle or a competition where the winner has to sacrifice a lot. Maybe it could be set in a fantasy world where a hero defeats the big bad, but in doing so, destroys half of the kingdom. This would lead to a complex story of rebuilding and dealing with the consequences.
A Cadmean victory fanfic could center around a character who wins a political struggle. However, they end up alienating a large portion of the population or losing their own moral compass. The story could then delve into how they try to regain the trust of the people or find their way back to their true self. It could be a character - driven exploration of the concept of victory at all costs.