One great 'Batwoman Supergirl' fanfic is 'Allies in the Shadows'. It has an interesting plot where they team up to fight a new villain in Gotham. The characterizations are on point, making it a really engaging read.
A good 'Batwoman Supergirl' fanfic often has strong character development. For example, showing how their personalities clash and then meld as they work together. This adds depth to the story.
Perhaps in this fanfiction, Supergirl and Naruto meet during a crisis that involves both their universes. Supergirl's super strength and flight could complement Naruto's speed and stealth. They could start off as rivals, each thinking their way of doing things is better. But as they face challenges together, they would come to respect each other. Naruto could use his shadow clone jutsu to create diversions while Supergirl uses her heat vision to take out enemies. Eventually, they become friends and vow to protect both their worlds.
Well, she might show off her super strength and flight abilities to the Avengers. They could be both impressed and a bit wary at first. Maybe she'd team up with Thor and they'd have a friendly competition about who can fly faster or hit harder. Then she could also share her knowledge of different threats from her own universe with the Avengers, and together they could come up with new strategies to face common enemies.
In a 'Supergirl meets the Flash fanfiction', they might team up to fight a powerful common enemy. For example, a super - villain who can manipulate time and space, and only their combined powers can stop him.
Supergirl is incredibly powerful with her Kryptonian powers. She can move at super - speed, has super - strength that can level buildings, and her heat vision can cut through almost anything. But Naruto is no slouch either. His nine - tailed fox chakra mode gives him a huge boost in power. He can also use Rasengan and other powerful jutsus. If they were to fight in an open area, Supergirl's flight might give her an advantage. But if it was a more strategic battle, Naruto could outwit her with his ninja skills.
Lex Luthor would be a great choice. He could be causing trouble in Gotham as well as Metropolis. His intelligence and resources would pose a significant threat to both Supergirl and Batman. He might be trying to manipulate events to make the two heroes fight each other so he can carry out his evil plans.