Harry Potter could visit Snape in the hospital. Despite their past differences, Harry might feel a sense of obligation or curiosity. He could be there to finally have an honest conversation with Snape and perhaps gain a better understanding of his actions throughout the years.
Another way Snape could comfort Harry is by standing up for him in certain situations. Maybe when other teachers or students are being unfair to Harry, Snape steps in and defends him. This act of protection can be a great source of comfort for Harry, as it shows that someone is on his side even if they have had a rocky relationship in the past.
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.
Snape could initially be skeptical. Given their long - standing enmity, he might not believe that Harry's apology is sincere at first. He might respond with a cold glare or a sarcastic comment, like 'Potter, your apologies are as empty as your head.'
To evaluate Snape's characterization, look at how his loyalty is portrayed. In the original series, he was loyal to Dumbledore but also had a complex past with Voldemort. His relationship with students, especially those in Slytherin, should also be considered. If he's too soft or too harsh compared to the books, it might be a sign of poor characterization.
There could be other Death Eaters that Snape knew in his life. In the afterlife, they might be there to either confront him about his double - agent status or to seek redemption themselves. And sometimes, characters from Snape's childhood, like his parents or childhood friends, might appear to add more depth to his backstory and his experiences in the afterlife.
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.
In some fanfictions, Snape kills Dumbledore as part of a greater plan. Maybe Dumbledore was already dying or had some sort of incurable dark magic on him, and Snape's act was a mercy killing. It could also be a complex plot twist where Snape is actually trying to protect the wizarding world from a greater threat that only he and Dumbledore knew about.
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.
In many such fanfictions, Dumbledore might comfort Snape by reminding him of his good deeds. For example, he could say that Snape's role as a double agent is crucial for the greater good. Dumbledore might also offer a sympathetic ear, listening to Snape's inner turmoil about his past actions and his love for Lily. By validating Snape's feelings and his importance in the fight against Voldemort, Dumbledore provides comfort.