Well, if the Sith were more powerful, it could lead to a complete shift in the balance of power in the galaxy. Maybe the Jedi would struggle even more to maintain peace and justice.
The Darth Revan story is quite outstanding. Revan was such a powerful and complex figure. His journey from a great Jedi to a Sith Lord and then back to a more ambiguous state was full of mystery. His influence on the SWTOR universe is huge, and his story has elements of redemption, power struggle, and the exploration of the Force that make it a standout among Sith stories.
Perhaps there are some neutral characters who get caught in the middle of the conflict between the Sith and the Jedi. They could be ordinary people, or they could be some other species in the Star Wars galaxy that are trying to survive the chaos that the Sith Lords bring with their power - hungry ways.
In Naruto Sith Lord fanfiction, a great plot twist might be that Naruto's friends secretly join him in his Sith - like ways, thinking they can control the dark side. Or perhaps Naruto finds out that the Hokage have been hiding knowledge of the Sith all along. It would also be interesting if Naruto uses his Sith powers to bring back dead characters, but they come back with a dark and unpredictable nature.
I think the character interactions would be the most interesting. Naruto as a Sith Lord would interact differently with his friends and foes. His relationships with Sasuke, Sakura, and Kakashi would be completely transformed, adding a whole new layer of drama to the story.
One more is Lord Malak. He's not as well - known as some other Sith Lords, but in fanfiction, he's often portrayed as a strategic genius. He's able to outwit his opponents in battle not just through his dark side powers but also through his understanding of military tactics. He's constantly plotting to expand the Sith Empire's territory.
Rey is the most prominent character as the fanfictions are often centered around her and the Sith. Luke Skywalker can be quite popular too. He can be a guiding figure for Rey, or in some fanfictions, he has a different view on the Sith and Rey's potential connection to them. Maul is also a favorite. His unique look and his own journey in the Star Wars lore make him an exciting addition to stories involving Rey and the Sith. Writers might have Maul's spirit or some remnant of his power interact with Rey as she delves into the world of the Sith.
The Sith Order began with a group of Force - sensitive beings who turned to the dark side of the Force. They were exiled from the Jedi Order or chose the path of the dark side on their own. The first Sith Lords developed their own teachings and ways of using the dark Force powers, which were often centered around domination and self - gain.