In some fanfictions, Loki's possessiveness of Peter can be seen in the way he protects him. He'll go to great lengths to keep Peter out of harm's way, but not just because it's the right thing to do. It's also because he sees Peter as his own. He might be overbearing at times, not allowing Peter to take risks on his own, which shows his possessive nature.
One way Loki can be possessive of Peter in fanfiction is through his magic. He could use his magic to keep an eye on Peter at all times. He might mark Peter in some magical way that only he can sense, so he always knows where Peter is. And if anyone tries to get too close to Peter, Loki will use his magic to subtly drive them away, all because he has this strong sense of possessiveness towards Peter.
One reason could be that Loki sees something special in Peter. Maybe Peter has a unique power or a pure heart that Loki is drawn to, and he wants to keep that all to himself.
One example could be that Fe doesn't allow others to rewrite or modify the Naruto fanfiction they have created. They might be very strict about copyright and ownership, and get angry if someone tries to take credit for their work.
One example could be in a fanfic where Draco constantly tries to keep Ginny away from other male characters at Hogwarts. He might glare at anyone who gets too close to her during Quidditch matches or in the hallways.
One example could be a fanfiction where Hinata gets jealous whenever Naruto talks to other female characters. She might subtly try to keep Naruto's attention on her by always being by his side and giving disapproving looks when others approach him.
One way could be Loki as a teenager having to hide his true identity (like his powers or his heritage) from his peers at school, just like in many teen dramas where characters have secrets. Another example might be Loki having a crush on another character in the fan - created world, and all the awkwardness and excitement that comes with a first love, which is a very common teen - related plot.
He's often shown as very controlling. For instance, he might control the Lost Boys strictly because of his possessive nature. He sees them as his and wants to keep them in Neverland.
One example could be that the fanfiction focuses on Loki's relationship with Thor. It could show a more tender side of their relationship, like Loki secretly helping Thor out of a difficult situation while still maintaining his mischievous facade.
Another one to check out is 'Loki's Territorial Love for the OC'. In this fanfiction, Loki's possessiveness is more on the territorial side. He sees the OC as his, and he's not afraid to show it. The story has a good plot that weaves in elements of Norse mythology along with the relationship between Loki and the OC, making it a really immersive read.
One aspect to consider in 'possessive Tony and Peter fanfiction' is the nature of their relationship. It might explore themes of protection. Tony could be possessive in a way that he wants to keep Peter safe from the various dangers in the Marvel universe, like powerful villains.
Peter can be an antihero in fanfiction. An antihero is a complex character who doesn't fit the typical hero mold. Peter could be seen as one if he has a morally ambiguous code. For instance, he might work with characters who are considered bad by society but have their own good reasons. He may also be driven by revenge more than the greater good at times, which makes him an antihero in the context of fanfiction.