A plot where the female OC supersoldier has a premonition of a future disaster that only she can prevent. She tries to convince the Avengers, but they are skeptical at first. As she races against time to gather evidence and figure out how to stop it, she uncovers a conspiracy within the superhero community. Another idea is that she is the only one immune to a new super - weapon that is targeting the Avengers. So, she has to protect them while they work on a way to neutralize the weapon. And she could also have a personal vendetta against a particular villain who was involved in the cruel experiments of her supersoldier program.
She could be from a different dimension where the supersoldier program was much more extreme. When she arrives in the Avengers' world, she has powers that are both a boon and a danger. The Avengers have to help her control her powers while she helps them fight a new threat that has followed her from her dimension. Or perhaps she is initially a villain, created by a mad scientist to be a weapon against the Avengers. But she has a change of heart and has to prove herself to the team. Also, a plot where she goes undercover in an enemy organization as a double - agent could be interesting.
One plot idea could be that the female OC supersoldier is sent on a mission to retrieve a powerful artifact before the bad guys get it. Along the way, she has to team up with some of the Avengers she doesn't trust at first. Another idea is that she discovers a dark secret about the supersoldier program she was part of that has ties to an enemy of the Avengers. Or she could be framed for a crime she didn't commit, and the Avengers have to decide whether to believe her or not while she tries to clear her name.
To create a compelling female OC supersoldier in Avengers fanfiction, first, give her a unique backstory. Maybe she was part of a secret government experiment. For her powers, make them distinct but still in line with the supersoldier concept, like enhanced senses beyond the normal. Her personality should be complex. She could be tough on the outside but have a soft side, perhaps a love for art that shows her humanity. Also, think about her relationships with the existing Avengers. Will she clash with Captain America because of their similar origins or will they bond over it?
One idea could be an OC who has the power to time - travel in a unique way, not like the Avengers' method. They could accidentally disrupt the events of 'Endgame' further while trying to help. For example, they might create alternate timelines where different villains gain power. Another plot could involve an OC who is a long - lost relative of one of the Avengers. They show up during the final battle and use their hidden powers to turn the tide. And a third idea is an OC who is from a different dimension entirely and has knowledge of how to defeat Thanos more easily, but they have to convince the Avengers to trust them first.
One plot idea could be an Avenger taking in an OC (original character) who has unique powers but is scared to use them. The Avenger, like Thor, could teach the OC about courage and how to control their powers. Another idea is an OC who is a tech genius and gets adopted by Tony Stark. They work together on new Iron Man suit designs. A third idea is an OC with a dark past being taken in by Black Widow. She helps the OC face their demons.
One idea could be an OC who has the power to manipulate time like Pietro. They could team up with Pietro to save the Avengers from a time - trapped enemy. The OC might be from a different dimension where time works differently, adding an interesting dynamic.
One idea could be that your OC is a therapist hired by the Avengers to help Bruce Banner deal with his psychological issues related to the Hulk. This would involve deep emotional conversations between the two characters and a new perspective on Banner's struggle.
An interesting plot could involve an OC who has the power to communicate with animals. In the story, they use this power to gather intel on the villains' plans. The animals could provide information that the Avengers wouldn't be able to get otherwise, like the location of a hidden lair or the movements of enemy troops.
A great plot could be that the male OC has a past connection to one of the main Avengers villains. For example, he was experimented on by the same organization that created the Hulk. This leads to a complex situation where the Avengers don't know if they can trust him. Or, the male OC could accidentally time - travel and change a small event in the past that has major consequences for the present - day Avengers, and he has to fix it.
One idea could be a male OC who has the power to manipulate time. He could be from a different dimension where the Avengers failed, and he comes to this universe to prevent the same fate. He might initially be distrusted by the Avengers but gradually prove his worth as he helps them defeat a powerful new enemy that was also a threat in his own dimension.
Another interesting concept is an OC who is a scientist researching Venom's origin. They accidentally get infected and use their new powers to help the Avengers in a unique way. For example, they could have enhanced senses that allow them to detect threats before the Avengers even know they're there. They also have to struggle with the dark side of the Venom symbiote while trying to be a hero.