Well, in a fanfiction about a Flash - Supergirl crossover where Barry gets stabbed, it would create a great deal of chaos and emotional turmoil. The Flash is such a crucial figure in Central City, and his injury would leave a big gap. Supergirl would bring her own set of skills and a different perspective. She might be able to inspire the people of Central City in a way that Barry couldn't while he's injured. Also, the other metahumans in the city could either rise to the occasion or cause more problems in the power vacuum.
If Barry was stabbed in this crossover fanfiction, it could be a real turning point. His friends and allies, including Supergirl, would be in a race against time to save him. Cisco could try to vibe for a solution, while Caitlin would be using her medical skills. Supergirl, with her super strength and flight, might be the key to finding the attacker quickly.
In a fanfiction scenario where Barry is stabbed during a Flash - Supergirl crossover, it could lead to a lot of interesting plot developments. Maybe Supergirl would have to step up and use her powers in new ways to protect Central City in Barry's absence. She might have to team up with the other members of Team Flash more closely.
If Barry was stabbed, the story would change drastically. His speed is what often saves the day, so without it, the villains would have an upper hand. Supergirl would have to cover more ground and face tougher challenges alone or with less - experienced allies.
Perhaps in this fanfiction, Barry's death causes a rift in the multiverse. Supergirl then has to team up with other heroes from different universes to try and fix it. His death could be the start of a much larger threat that only a united front of heroes can face. She might struggle with the guilt of not being able to save him at first but then turns that into motivation.
If Barry kidnapped Supergirl in fanfiction, it could be a really interesting plot twist. Maybe Barry has been affected by some sort of red kryptonite - like substance that makes him act out of character. This would lead to a conflict between the Flash and Supergirl's friends and allies. They would be confused as to why Barry would do such a thing.
Another possibility is that Barry was kidnapped himself first and then forced to kidnap Supergirl. The real kidnappers could be a group of meta - humans who want to create chaos by pitting two of the most powerful heroes against each other. Barry would be in a difficult situation, having to do something against his will, and Supergirl would initially be confused and angry at Barry until they both figure out what's really going on.
One idea could be that a powerful villain threatens both their cities simultaneously. Supergirl and The Flash have to team up, and in the fanfiction, their different powers and personalities could lead to some interesting interactions. For example, Supergirl's strength and The Flash's speed could be combined in unique ways to defeat the villain.
A great moment could be when they first meet and realize how different yet similar their worlds are. Supergirl might be in awe of The Flash's speed, and The Flash could be impressed by Supergirl's strength. It's a moment of mutual respect that often sets the tone for the rest of the story.
If Barry dies in a fanfiction crossover, it could lead to a power vacuum. This might cause other villains to become bolder. For example, the Rogues might try to take over Central City without the Flash to stop them. Supergirl would then have to step in and deal with a situation she's not entirely familiar with, which could change the dynamics of how she operates in the DC Universe.
Another theme is the exploration of different universes. Sometimes the fanfictions will send the characters into alternate realities where they have to adapt and find their way back. This allows for a lot of creativity in terms of world - building and character development. Also, friendship is often a key theme. These heroes come from different shows but in the crossovers, they form strong bonds and support each other through tough situations.
One popular storyline is when Flash and Supergirl team up to fight a common enemy from another dimension. This allows for a lot of action and showcases their different powers working together.
Well, Cisco Ramon from The Flash would be a great addition. He could use his tech skills to create some new gadgets or figure out ways to counter the villains' powers. Also, Martian Manhunter from Supergirl's side. His shape - shifting and telepathic abilities would add a whole new dimension to the story.