In some versions, Lily could end up changing Snape's view on things while being kidnapped. Snape then decides to join the side of good more wholeheartedly and they form an unlikely alliance against the Dark forces. Lily forgives him for his extreme actions as she sees his good intentions beneath the wrong means.
Maybe Snape realizes the error of his ways and releases Lily. They have a long, heartfelt conversation where Snape finally confesses his true feelings in a non - possessive way and they part as friends, with Lily understanding his misguided attempt at protection.
It could end with Lily escaping and being forever angry with Snape. She might cut all ties with him and go on to marry James Potter, with Snape left full of regret for his actions.
Snape in 'Snape Saves Lily' fanfictions is typically depicted as a hero in a sense. Despite his past associations with the dark side, his love for Lily makes him turn against his former allies. He is shown to be intelligent and resourceful, using his skills in magic, especially his knowledge of potions and dark arts (but using it for good in this case), to save Lily from various threats. He is also portrayed as a very emotional character, his love for Lily being the one pure thing in his otherwise troubled life.
Often, it ends with Draco having a change of heart. He realizes the wrongness of his actions and releases Ginny. This could be due to seeing Ginny's vulnerability or her kindness towards him even in captivity. They might even become friends or something more in some cases. Another common ending is that Harry and his friends rescue Ginny. There's a big showdown where they outwit Draco and his accomplices and save Ginny.
In some versions, it might end with Chat Noir realizing his mistake. He could come to his senses, either on his own or with the help of a friend. Then he releases Marinette and they work together to solve the real problem that led to the kidnapping in the first place.
Well, perhaps Snape has some desperate reason. Maybe he's trying to protect Lily from the Dark Lord in his own twisted way. He might think that by taking her away from the wizarding world for a while, he can keep her safe from Voldemort's reach.
Well, it depends on the nature of the fanfiction. In some cases, the kidnapped character's friends or allies will come to rescue them. This can lead to a big battle or confrontation with sans. If sans is being controlled by someone else when he kidnaps, the rescuers might have to figure out how to free him from that control as well. Sometimes, the kidnapped character might also find a way to escape on their own, and then they have to decide whether to get revenge or try to understand sans's motives.
Snape might be initially in shock. He had trusted Lily deeply, so the betrayal would hit him hard. He could become very angry and bitter, perhaps vowing revenge against her. He might also close himself off emotionally, not wanting to trust anyone again.
In such fanfictions, Lily's forgiveness can make Snape seem more redeemable. It softens his otherwise prickly and often dark character. His actions might be seen in a new light, as if he is now more worthy of understanding and compassion because Lily, who he cared about deeply, has forgiven him.
It could also end with a more complex resolution. Loki realizes the error of his ways during the time he has Tony kidnapped. Maybe through their conversations, Loki sees the value in Tony's life and the good he does. So, Loki releases Tony and decides to help the Avengers in their fight against a common enemy as a form of redemption.
It could end with Snape realizing he was wrong. He apologizes to Harry and they form an unlikely alliance. They return to Hogwarts together and Snape has to face the consequences of his actions from Dumbledore.
There are versions where Snape reacts defensively. Let's say Lily confronts him about his actions that seem to be harming her or her friends. He would immediately start justifying himself, listing all the reasons why he did what he did, trying to make Lily see his point of view, even if deep down he knows he might be in the wrong.