Snape might use magic that he has mastered over the years. He could perform a spell that targets the specific harm Hermione has caused to herself while attacking him. For example, if she got injured by a backfiring spell, he could use a counter - spell to reverse the damage at a magical level.
Well, in some fanfictions, Snape might use his advanced potions knowledge. He could brew a special healing potion for Hermione. Maybe it's a modified version of a known potion, like the Essence of Murtlap that has strong healing properties.
One possible reason could be a misunderstanding. Maybe Hermione thought Snape was involved in some dark plot against her friends. In the wizarding world, there are often secrets and deceptions, and if she got some false information, it could lead her to take such drastic action.
One reason could be Snape's sense of duty. As a teacher at Hogwarts, he has a responsibility to look after the students, even if they attack him. So, he would put aside his personal feelings and help Hermione.
Dumbledore might come to Snape's aid. Dumbledore always had a somewhat complex relationship with Snape, and he would likely step in to prevent things from getting too out of hand. He could use his powerful magic to stop Hermione and then try to sort out the situation calmly.
In some fanfictions, Snape might use his advanced knowledge of potions to brew a special healing elixir for Harry. He could also use his magic skills, like a complex spell specifically designed to mend Harry's wounds, whether they are physical or emotional.
Snape could also use his magical abilities in a more emotional sense. He might share his own past traumas with Harry, creating a bond of understanding that starts to heal Harry's broken spirit. By being vulnerable himself, he shows Harry that it's possible to move past pain.
One great Snape and Hermione fanfiction is 'The Unbreakable Bond'. In this story, Hermione discovers a hidden side of Snape during her research in the Hogwarts library. Their relationship starts as a mentorship but gradually evolves into a deep friendship that defies the expectations of the wizarding world. It beautifully portrays their individual characters and how they can complement each other.
The 'time - travel' trope is also quite common. For example, Hermione might go back in time and interact with a younger Snape, which can lead to all sorts of new storylines and character developments.
Snape might initially be shocked. He's not one to show much emotion openly, but internally he could be very disturbed. He might start investigating what happened to Hermione immediately, using his skills in potions and magic to try and find a cure or at least understand the cause.
This could be a modern AU (Alternate Universe) fanfiction where the magical setting is replaced with a contemporary one and Snape takes on a non-magical job like being a bartender.
Well, Snape might heal Draco because of his own sense of morality. Despite his dark exterior, Snape has a code of ethics. Draco is still a student, and Snape may believe that every student should be given the chance to survive and learn from their mistakes. Additionally, Snape could be acting on behalf of Dumbledore in some way. Dumbledore often had complex plans, and Snape was his agent. Healing Draco could be part of a bigger plan to keep the balance in the wizarding world.