In 'Kidnapped Love' Twilight fanfiction, it could be that a vampire kidnaps a human for some dark or misunderstood reasons. This could lead to a complex exploration of the vampire - human relationship. The kidnapped person might initially be terrified but then start to understand the kidnapper's motives, which could be related to love in some convoluted way.
It could be a new vampire who is jealous of Edward's relationship with Bella. This vampire might be from a far - off place and has heard about the Cullens and Bella. They decide to kidnap Bella to make Edward suffer. Another possible antagonist could be a human who has a grudge against the Cullens. Since Bella is associated with them, they target her. For example, a human whose family was attacked by a vampire in the past and blames the Cullens for not preventing it. They think that by kidnapping Bella, they can get back at the Cullens.
In 'Kidnapped by a Creeper Twilight Fanfiction', perhaps the creeper is from the Minecraft world and the Twilight aspect adds a unique twist. The kidnapped character may find themselves in a strange hybrid world. They could start to discover new abilities or traits that are a blend of the two universes. For example, they might have the speed of a Twilight vampire to outrun the creeper at times. There could also be a love interest that emerges during the struggle to escape.
One possible plot could be where a secondary character from the Twilight series is kidnapped by a new vampire clan that wants to use them as a bargaining chip against the Cullens. This could lead to a series of tense negotiations and action - packed rescues.
It could be Discord. He loves causing chaos and kidnapping Twilight Sparkle would be a great way to disrupt the harmony in Equestria. He might do it just for fun or to see how Twilight's friends would react.
One idea could be that a new vampire clan kidnaps Bella to use her as bait to lure Edward into a trap. They might want to challenge the Cullen family's power in the vampire world.
In some fanfictions, Bella might be kidnapped by a new vampire species that is trying to understand the relationship between humans and vampires. They see Bella as an important specimen since she is so deeply involved with the Cullens. So, they take her away to run tests on her, not with any malicious intent initially but more out of scientific curiosity. Another idea is that a witch or a magical being in the Twilight universe kidnaps Bella. They might believe that Bella's connection to the vampires has some sort of magical significance that they can use for their own gain. For instance, they could think that her blood has some special property that can enhance their magic. A more simple plot could be that a human who is jealous of Bella's relationship with Edward kidnaps her. This human might be someone who has a crush on Edward and thinks that by getting rid of Bella, they can have a chance with him.
Perhaps it could be a minor character from Twilight who somehow ends up in a situation where they are kidnapped by a creeper. This would give the writer a chance to explore that character more deeply and in a completely different context. For example, a character like Jessica from Twilight could be the main character. She's not a central figure in the original story, but in this fanfiction, she could have a whole new adventure.
It could be a rogue vampire who wants Bella for her unique blood. There are many vampires in the Twilight world who might be tempted by her smell. Another potential kidnapper could be a vengeful werewolf who blames Bella for something, perhaps for the way the vampires and werewolves' relationship has changed. It might also be a human who has somehow found out about the vampire world and thinks they can use Bella to gain power or knowledge.
One possible plotline could be that Twilight Sparkle is kidnapped by a powerful dark magic user who wants to steal her knowledge of magic. Her friends then embark on a quest to rescue her, facing various challenges along the way. Another could be that she is kidnapped by an unknown force from another dimension for some sort of experiment. Her friends have to figure out how to cross dimensions to save her. A third plotline might be that a group of villains kidnap Twilight Sparkle to use her as a bargaining chip against Equestria, and her friends must find a way to outwit the villains and get her back safely.