The Resident Evil characters are used to dealing with limited resources and a survival - horror environment. The Kingdom Hearts characters, on the other hand, are more used to a more fantastical and adventure - based combat. In a crossover fanfiction, the Kingdom Hearts characters could learn from the Resident Evil characters' resourcefulness. At the same time, the Resident Evil characters could gain new powers or abilities from the Kingdom Hearts world, like the ability to travel between worlds or use magic. This exchange of abilities could lead to some really exciting and unexpected combat scenarios.
Naruto's Rasengan could be used in interesting ways. For example, if he combines it with the Resident Evil knowledge of bio - energy, he might be able to create a Rasengan that can destroy the mutated cells of the bio - weapons more effectively. And for characters like Chris Redfield, his combat skills and experience with firearms could be enhanced by learning some basic ninja moves from the Naruto characters, like how to move stealthily.
Ruby's speed and scythe - wielding skills could be enhanced by the Keyblade's magic. For example, she could use the Keyblade's power to make her Crescent Rose even more powerful, like adding elemental attacks. Sora's ability to quickly adapt to new situations and his combat skills with the Keyblade could be combined with the Huntsmen training in RWBY. He could learn new fighting styles from the RWBY characters and they could learn from his experience with different enemies. Donald and Goofy's support abilities could be used to assist the RWBY teams in battles, like Donald's magic for healing or Goofy's defense - boosting skills.
Well, Sora's ability to use the keyblade could be combined with Scrooge McDuck's combat skills. Scrooge is quite a fighter, and with Sora's keyblade, they could make a formidable team. For example, Sora could use his magic spells while Scrooge uses his cane to fend off enemies.
Sasuke's sharingan would be a very useful ability in the Resident Evil world. He could use it to quickly analyze the movements and weaknesses of the mutated creatures. In return, Resident Evil characters could teach the Naruto characters about modern weaponry. For instance, Ada Wong could show Sakura how to use a grappling hook gun, which Sakura could then incorporate into her combat style along with her medical ninjutsu. Also, Naruto's rasengan could be enhanced with some Resident Evil technology, like using a virus sample to make it more deadly against bio - enemies.
One creative plot could be the characters from Kingdom Hearts finding themselves in the Resident Evil world. Sora, Donald, and Goofy might have to use their Keyblades against the zombies and bio - organic threats. They could team up with some of the Resident Evil protagonists like Leon or Jill to find a way back to their own world while also trying to stop a major outbreak.
For Naruto, his shadow clone jutsu could be combined with a Stand's ability. Imagine his clones also having the power of a Stand. So, if he has a Stand like Star Platinum, all his clones could use Star Platinum's super strength and speed. In the case of Jojo characters, someone like Josuke Higashikata could use his Crazy Diamond to repair ninja tools or even heal ninja injuries. His ability to fix things could be really useful in the Naruto world where battles often lead to broken equipment and injured comrades.
The Keyblade wielders like Sora, Riku, and Kairi would bring a sense of adventure and a different kind of magic to Equestria. The ponies, on the other hand, could teach them about the power of friendship in a more direct way. Donald and Goofy might be a bit startled by the ponies at first but would soon get used to them. Donald's magic could be compared to the magic of some of the unicorn ponies, and they could exchange magical knowledge.
Sora would likely be very protective of Ariel. He would see her as someone in need of help, just like he does with many characters in different worlds. Ariel, on the other hand, would be fascinated by Sora's world and his Keyblade. She might ask him a lot of questions. Donald could get frustrated with Ariel's overly curious nature at times, while Goofy would just be friendly and go along with whatever is happening.
If we consider the more heroic characters from Resident Evil like Leon, he might try to form an alliance with the gargoyles. He could see their potential in fighting the bio - hazards. The gargoyles, in turn, might be hesitant but could be swayed by Leon's determination. The villains from Resident Evil, such as Wesker, would likely see the gargoyles as something to be either controlled or destroyed, which would create a lot of conflict in the story. And the gargoyles would not take kindly to being manipulated.