Sakura would be a likely candidate. As a skilled medical ninja, she has the knowledge and ability to diagnose the poison and attempt to create an antidote.
It's also possible that Naruto could save himself. With his strong will and the power of the Nine - Tails, he could potentially find a way to overcome the poison. He has shown in the past that he can endure great hardships and come out on top.
Tsunade could also be the one to save Naruto. She is the best medical ninja in the village and has vast experience in dealing with various poisons and injuries. She might use her strength and medical expertise to fight off the poison in Naruto's body.
Sakura could be the one to save Naruto. She is a skilled medical ninja. She could use her medical jutsu to keep Naruto alive even while he is crushed. Then, with the help of others like Kakashi, they could figure out a way to remove the rock and fully heal Naruto.
Perhaps an enemy from a rival group. They might see Sakura as a threat to their plans, so they poison her to get her out of the way. Another possibility is a character who has been secretly harboring a grudge against her for a long time, and finally decides to take action by poisoning her.
It could be a team effort. Amy with her determination, Tails with his intelligence, and Knuckles with his strength could all come together. They might search different places for the cure ingredients. Amy could search in the forest for a rare flower, Tails could look in his lab for a chemical compound, and Knuckles could dig for a special mineral. All these combined might save Sonic.
In 'naruto gets stabbed fanfiction', it might be a new enemy that has emerged, someone with a powerful and unknown jutsu. This enemy could see Naruto as a threat to their plans and decide to stab him to eliminate him. Or it could be a character who has been corrupted by dark power, like a former friend or ally who has fallen to the dark side and no longer recognizes Naruto as a friend.
Sakura could potentially be Naruto's girlfriend in some fanfictions. Although in the original series she had feelings for Sasuke for a long time, in fan - created stories, the writers might explore a different path where she realizes Naruto's true worth and they end up together.
He could marry Mikasa from Attack on Titan. Just think about it. Naruto's positive and determined personality would contrast with Mikasa's more stoic and protective nature. They could meet through some sort of interdimensional accident. Naruto would be fascinated by the Titans and the world outside his own, and Mikasa might be intrigued by Naruto's ninja abilities.
It could be Sakura. In the original series, their relationship was complex, and in fanfiction, it would be a common choice for her to be the one to dump Naruto, perhaps due to her still having feelings for Sasuke.
He could marry Hinata. Even though he's banished, Hinata might follow him because of her deep love for him. Their relationship could develop further outside the village, and they could get married and start a family.
Kakashi could also play a role. He has always been a mentor to Naruto and his sense of duty and loyalty to his student might drive him to search for Naruto when he hears that he's been left for dead. He has the skills and knowledge to find and save Naruto in a difficult situation.
Iruka Sensei could be a likely candidate. He already has a close bond with Naruto and cares for him deeply. Adopting Naruto would be a natural extension of that relationship, and he could provide Naruto with a stable home life and continue to mentor him in his ninja training.