Another possibility is that there could be a new character introduced who is pulling Theo's strings from the shadows. This new character has a vendetta against Lydia or the pack and uses Theo as a pawn in their evil plan. So this mystery character would be the main antagonist in a more complex way.
It could also be an unseen force controlling Theo. In this case, the real antagonist is this hidden entity that uses Theo to kidnap Lydia. The story could then be about Lydia and her friends not only rescuing her from Theo but also uncovering and defeating this greater threat.
Another plot could be that Theo kidnaps Lydia as a way to get back at the McCall Pack. Since Lydia is an important member of the pack, taking her would be a major blow. As she's held captive, Lydia discovers Theo's deeper motives which are related to some past event involving her friends. This could lead to a tense stand - off when the pack comes to rescue her.
It could be a new character introduced in the fanfiction. Maybe a powerful witch who has the ability to manipulate emotions. She targets Stiles and makes him stop caring as part of her evil plan to disrupt the balance in the town. Since Stiles is an important part of the group, his change in attitude would cause chaos.
In this fanfiction plot, Theo kidnaps Lydia because he believes she can help him get revenge on someone. He takes her to a secluded location. Lydia is angry as well as frightened. She starts to play mind games with Theo, using her intelligence. Theo is taken aback by her resilience. As they interact more, Theo starts to see Lydia not just as a means to an end but as a person. This change in his perception makes him question his actions. At the same time, Lydia is constantly looking for an opportunity to send a signal to her friends so that they can come and rescue her.
There might be a jealous friend or acquaintance who feels that Stiles, as a girl, is getting too much attention. This person could then start spreading rumors or causing trouble for Stiles in an attempt to bring her down.
Perhaps a rogue werewolf pack. They see Stiles as a threat because of his nine - tailed fox powers. They believe that his existence could disrupt the balance of power in the supernatural world. So, they constantly try to hunt him down and drive him out of the town. They might also target his friends to get to him.
Title: 'The Abduction of Lydia by Theo'. In this fanfiction, Theo might have his reasons for kidnapping Lydia. Maybe he believes she holds the key to some power or knowledge he desperately wants. He could be a complex character, not entirely evil, but driven by his own motives. Lydia, on the other hand, would be a strong - willed victim. She'd use her wits to try and outsmart Theo, leading to a tense cat - and - mouse game throughout the story.
Well, in Stiles and Theo kiss fanfiction, it often explores a different side of their relationship. Maybe it's a way to show a deeper connection that wasn't fully explored in the original show. It could be a creative way for fans to express their desires for these two characters to have a more intimate bond.
Perhaps they find out they're pregnant unexpectedly. Stiles starts making all these plans for their future as a family right away. Lydia is more cautious, thinking about how this will change their lives completely. Their friends could also play a big role, some being super supportive while others might be skeptical. And they could have to deal with family reactions, like Stiles' dad being really excited and Lydia's parents having mixed feelings.
It could be an old nemesis from Stiles' past, someone who has always been a thorn in his side.
It could be another vampire clan. Maybe they are jealous of the Cullens' interest in Bella or they think that Bella's presence among the Cullens will disrupt the balance of power among vampires. So they try to get Bella from the Cullens, making them the main antagonists.