Maybe it's a criminal mastermind that Drake has been getting too close to in his investigations. This person sees Drake as a threat and decides to kidnap him to halt his progress. It could be someone who has a lot to lose if Drake exposes their illegal activities, like a powerful underworld figure running a large - scale smuggling operation.
It could be an old acquaintance from his past who has turned to the dark side. Maybe someone he once trusted during one of his earlier adventures but who has since become jealous of Drake's success and wants to use him to get rich quick. For example, a former partner who was left behind in a previous treasure hunt and now blames Drake for his misfortunes.
Perhaps Drake is kidnapped because he has uncovered a dark secret in Ripper Street. The kidnappers could be trying to silence him. His captors might hold him in an abandoned building, and he has to use his wits to try and escape while his colleagues search the seedy underbelly of the street for him. This could involve a lot of tense moments as the kidnappers threaten him and his friends get closer to finding him.
It could be a secret society that has been observing their actions and sees them as a threat to their hidden agendas. This society might have members with special skills and resources to carry out the kidnapping.
A group of outcasts from different islands might kidnap Moana. They feel that they have been wronged by the 'normal' society that Moana represents. They hope that by kidnapping her, they can get the attention they deserve and force the islands to change their ways. But Moana listens to their grievances and tries to find a way to help them while also finding a way home.
It could be Zeref. Since Zeref has an interest in powerful magic users and Natsu is a strong dragon slayer, Zeref might kidnap Natsu to study his magic or use him in some dark plan related to his quest for immortality or power.
It could be a jealous rival from his own village. Maybe someone who is envious of Shikadai's natural talents and popularity, so they decide to kidnap him to get him out of the way.
It could be an envious rival. Maybe someone who's always been in the shadow of Osomatsu and his brothers and decides to take matters into their own hands by kidnapping Osomatsu. Another option is a deranged collector. This person might see Osomatsu as a rare item to add to their collection of oddities. Or it could be a vengeful spirit. In a more supernatural setting, a spirit with a grudge against the Matsuno family could kidnap Osomatsu as a form of revenge.
It could be a rogue werewolf. Maybe this werewolf has a grudge against Stiles' pack and thinks that by kidnapping Stiles, he can get some sort of revenge or leverage.
Well, it could be an envious maid from the palace. She sees Cinderella getting all the love and attention from the prince and decides to kidnap her. Maybe she thinks that if Cinderella is out of the picture, she can win the prince's heart. Or perhaps it's a dark wizard who has been observing Cinderella from afar. He wants to use her pure heart for some dark magic ritual, so he kidnaps her. There's also a chance that it could be a group of outlaws who heard about Cinderella's new wealth and status and think they can get a big ransom for her.
It could be Frieza. He might see Bulma as a valuable asset due to her intelligence and knowledge of Earth's technology. He could kidnap her to use her to build powerful weapons or devices to help him regain his power and dominance in the universe.