A more complex plot could be Loki impersonating Black Widow. He infiltrates the more covert operations of the Avengers. While in her form, he could plant false intelligence, leading the Avengers into dangerous situations. He could also use her relationships with the other members, like Hawkeye, to create emotional turmoil within the team, all while trying to achieve his own goals of taking over the world or getting his hands on powerful magic items.
If Loki impersonated Thor, the real Thor would be furious when he found out. The other Avengers, like Iron Man, might initially be confused but then quickly realize something is off. Iron Man would likely use his technology to detect the impostor. Hulk might just smash first and ask questions later when he senses something wrong with 'Thor'.
Well, a cool plot could be Darcy discovers a hidden power within herself while being around Loki. Loki, intrigued by this, decides to help her master it. Along the way, they face challenges from both Asgard and Earth. Maybe some Asgardians think Darcy is a bad influence on Loki and try to separate them. Meanwhile, on Earth, SHIELD is also suspicious of their alliance. It could lead to a lot of action and some unexpected friendships and romances.
One plot idea could be that Loki has been captured by a powerful new enemy who wants to use his knowledge of Asgardian magic. The Avengers find out and embark on a rescue mission. Along the way, they face various traps set by the enemy. Another could be that Loki fakes his own capture to draw out a threat that he can't handle alone, and the Avengers come to his aid not knowing it's a ruse at first.
A plot could involve Loki using his agent skills to manipulate the Avengers into a false sense of security. He then reveals a master plan that involves using their own powers against them to take over Earth. But in the process, he starts to have second thoughts as he gets to know the Avengers better and forms unexpected friendships. For example, his interactions with Black Widow could lead to him seeing the value in human relationships.
One idea could be that Loki gets turned into a vampire while in the midst of his schemes against the Avengers. This new state gives him different powers and motives. He might struggle with his newfound thirst and also use his vampire abilities to outwit the Avengers in different ways.
One idea could be Loki's struggle to hide his condition from the other Avengers. He might be worried about how they'll react, especially Thor. Another plot could involve a character, perhaps a new Asgardian healer, trying to find a way to ease Loki's discomfort during this time.
In a 'gabriel is loki avengers fanfiction', the plot could start with Gabriel being mysteriously drawn to Loki's presence. He could be an angel - like being who is intrigued by Loki's mischievous nature. The Avengers, on the other hand, see Gabriel as a potential threat because of his association with Loki. As the story progresses, Gabriel could try to prove his good intentions to the Avengers while also trying to figure out Loki's true intentions. There could be a lot of internal struggle within Gabriel as he battles between his loyalty to Loki (if there is some pre - existing bond) and his desire to do what's right for the world. This could lead to a complex web of relationships and a story full of twists and turns as Gabriel tries to navigate the world of the Avengers and Loki.
It could be that Loki is in emotional pain due to being rejected by Asgard again. He's alone and suffering. The Avengers, especially those like Black Widow who understand the pain of being an outcast, reach out to him. They discover that an old enemy is planning to use Loki's vulnerable state to launch an attack on both Asgard and Earth. So they have to protect Loki and stop the enemy at the same time.
Loki could be injured while exploring a dangerous new realm. He's attacked by strange creatures and sustains a life - threatening injury. His journey to recover could involve him having to rely on a local healer who has a very different view of magic from his own. This forces him to adapt and learn new ways to heal.
Maybe the Avengers are trying to prevent a powerful artifact from being misused. Loki, who has a history with artifacts, offers his assistance. He might do this to gain some sort of favor from the Avengers or because he realizes the consequences of the artifact falling into the wrong hands. In the fanfiction, he could use his trickery to steal the artifact back from the villains before they can use it.