One interesting plotline could be Hermione using her vast knowledge of magic to outwit a powerful dark wizard who has everyone else under a spell. She might find a long - forgotten spell in the library that can reverse the dark magic.
One possible plotline could be that Harry uses a powerful spell he's been secretly practicing to stun Bellatrix just in time as she's about to harm Hermione. For example, he might use a modified version of the Stupefy spell that's more powerful. Another could be that Harry manages to create a diversion, like summoning a horde of magical creatures, which distracts Bellatrix long enough for him to rescue Hermione.
One interesting plotline could be Snape's internal struggle as he tries to save the Potters. He has complex feelings towards James Potter, yet his love for Lily drives him to protect the family. Maybe he has to outwit Voldemort's inner circle without revealing his true intentions.
One interesting plotline could be Naruto having to team up with unexpected allies from different villages to save the world. Maybe he has to work with some of the old villains who have a change of heart due to a greater threat.
Well, perhaps the OC is in a life - threatening situation like being trapped in a collapsing cave during a battle. Naruto, being the hero he is, uses his shadow clone jutsu to search for and rescue the OC. Or maybe the OC is being mind - controlled by an enemy, and Naruto has to find a way to break the control and save the OC. It could involve a lot of action and some emotional moments as Naruto tries to reach the OC's true self.
Perhaps Merlin has to save the knights from a curse. He could go on a long journey to find the ingredients for an antidote while facing many obstacles along the way. He might have to outwit evil spirits or solve difficult riddles to get what he needs to break the curse on the knights.
Another interesting plotline could be related to the prophecy or some sort of hidden danger that only Shanks is aware of. He saves Luffy not just from an immediate threat but from a long - term danger that could have ended Luffy's journey towards becoming the Pirate King. Shanks might have to sacrifice something of his own in the process, like his position or a precious item, to ensure Luffy's safety.
One possible plotline could be Damon using his vampire abilities in a unique way to rescue Bella from a dangerous situation, like a group of rogue vampires. Maybe he uses his speed and strength to fight them off.
Some fanfictions explore a different relationship dynamic between them. Maybe Harry has a problem that only Hermione can understand and help him with, and this brings them closer in a way that's different from their normal friendship. It could be something related to his connection with Voldemort or his family history.
One interesting plotline could be Hermione's journey of self - discovery within the pack. Maybe she discovers new magical abilities or a deeper understanding of her own strength as she interacts with the pack members.
One interesting plotline could be Hermione's struggle to hide her maledictus condition from her friends at Hogwarts. She might constantly worry about turning into the beast associated with the curse and how it could endanger those around her.