Dr. Bruce Banner could play an important role. His scientific knowledge could be used to analyze Captain America's condition and come up with solutions. In some fanfictions, he might even find a way to enhance Captain America's healing abilities. Also, Thor, if he's around, could use his Asgardian magic or knowledge to help in the healing process, perhaps by bringing some rare Asgardian herb or elixir that has healing properties.
Hermione would definitely be one of the first to help. She's extremely intelligent and well - read in magic, so she'd quickly start looking for spells or potions to heal Harry. She'd also stay by his side to comfort him and keep his spirits up.
Nobara Kugisaki and Megumi Fushiguro could also be among those who help. Nobara is a strong - willed and capable sorceress. She would be concerned about Nanami's well - being and use her skills to assist him. Megumi, being a calm and intelligent sorcerer, would likely come up with a plan to rescue or heal Nanami. They all share a sense of comradeship within the Jujutsu Kaisen world.
Lisbon would probably be the first one to help. She has a deep connection with Jane and cares about his well - being.
Even some of the antagonists could potentially help Jaune if there is a complex relationship developed in the fanfiction. For example, if an enemy realizes that Jaune's death or continued injury would disrupt some sort of balance, they might step in to heal him, albeit reluctantly.
Maybe it's a new villain who is trying to make a name for themselves. This villain could see shooting Captain America as a way to gain instant notoriety in the criminal underworld. They might have studied Captain America's weaknesses and found an opportune moment to strike.
His butler, Kuroba Toichi, if still alive in the fanfiction world, would surely come to his aid. He has a lot of experience and resources, and his loyalty to Kaito Kid would make him a natural choice to help him when he's hurt, whether it's by providing medical assistance or getting him out of a dangerous situation.
Bobby could also be a key figure. He's like a father figure to the boys and has a wealth of knowledge. He might know of some old remedies or be able to point them in the right direction to find a way to heal Dean. Charlie could also pitch in. She's smart and resourceful and could use her hacking skills to find information related to Dean's injury.
Erak might be an unexpected character to help. Despite his rough exterior, he has a sense of honor. If he happened to be in the area when Will gets hurt, he could offer his ship as a means of quick transport to a place where Will can be treated. Also, the apprentices that Will has trained. They would look up to him and would be eager to repay his kindness. They could run errands, gather herbs for medicine, or keep watch while Will recovers.
Alex is very likely to be one of the first to help Kara. As her sister, she has a deep bond with Kara and would do anything to protect her. Alex has medical training and combat skills, so she can both treat Kara's injuries and defend her if needed. Another character would be Winn. He is a tech - genius and could use his knowledge to create something to help Kara heal faster or to find a way to counter whatever caused her injury. Also, J'onn J'onzz, with his shape - shifting and telepathic abilities, could be a great asset in protecting Kara while she's injured and in helping her recover mentally as well as physically.
One likely character would be her closest friend. This person would be by her side immediately, providing emotional support and maybe even some basic first - aid if they are able. They would stay with her throughout her recovery process, being a source of comfort.