In such a fanfiction, it could lead to some major plot twists and character developments. The Avengers' loyalties and actions would likely be completely different.
Betrayal is a common theme. For example, an Avenger might be secretly a Hydra agent, leading to a sense of betrayal among the team members.
Perhaps in the 'avengers of hydra fanfiction', Hydra has developed a new super - weapon that can neutralize the Avengers' powers one by one. The story could follow the Avengers as they scramble to find a way to counter this weapon while also dealing with Hydra's attacks on various cities. Or, there could be a plot where a powerful Hydra agent uses magic to possess some of the Avengers and make them do Hydra's bidding, and the remaining Avengers have to find a way to break the spell.
Definitely the Avengers members like Captain America, Iron Man, Thor, Hulk etc. would be main characters as they are the core of the Avengers. On the Hydra side, characters like Baron Wolfgang von Strucker could be prominent. Also, there might be some original characters created specifically for the fanfiction, perhaps a Hydra scientist who is behind a new and dangerous experiment targeting the Avengers.
One idea could be a crossover where Hydra discovers the wizarding world in the Harry Potter universe and tries to use magic for their evil purposes. The Avengers somehow get wind of this and team up with Harry Potter and his friends to stop Hydra. Maybe they have to battle magical creatures that Hydra has corrupted with dark magic.
One great Avengers fanfiction to watch next could be 'The New Avenger'. It has an interesting plot where a new hero emerges and has to prove themselves to the established Avengers. The character development is really well - done.
Well, a possible plot could be that the Hydra experiment was actually a cover - up for a much larger and more sinister plan. The Avengers discover that the experiment was just the tip of the iceberg and they have to race against time to stop Hydra from unleashing something far worse. It could also be interesting if the experiment somehow gives an ordinary person the ability to see into the future, and that person becomes a key figure in the battle between the Avengers and Hydra.
A really interesting one is 'Avengers vs Hydra: A New Perspective'. It presents a different view of the age - old conflict. Instead of the usual fight, it explores the idea of some Avengers having a more nuanced view of Hydra and how that affects their actions and the overall dynamic within the team.
Fanfiction explores it in many ways. For example, some might show a reluctant alliance between an Avenger and a Hydra operative for a common goal. This shows that the relationship is not always black and white.
The Avengers would likely be very protective of her at first. For example, Thor might use his strength to keep her safe from any immediate threats. Iron Man could use his technology to check if she has any tracking devices on her or if she's been poisoned by Hydra.
In the fanfiction, it might be that the little girl is a key to unlocking some secrets of Hydra. The Avengers, in their quest to dismantle Hydra completely, stumble upon her. She could hold the knowledge of hidden Hydra bases or their future plans. So they take her in to figure out how to use this information against Hydra.