A possible plot idea is that Captain America is brainwashed into thinking he's from another dimension and has a different set of loyalties. He then starts to work for an alternate version of a villain. As he's brainwashing, he could be used to infiltrate S.H.I.E.L.D. and disrupt their operations from the inside. The story could focus on his teammates trying to figure out what's wrong with him and how to reverse the brainwashing, while also dealing with the damage he's causing.
One plot idea could be that after being brainwashed, Captain America is made to believe his old friends are enemies. So he starts targeting the Avengers. Another could be that he is brainwashed to carry out a secret mission that goes against his moral code, like stealing important artifacts for a shadowy organization. And he has to struggle to break free from the brainwashing when he starts to have flashes of his true self.
It might not be exactly what you need, but I'll try my best to recommend a novel that is most relevant to your description: "Beautiful Man: I, a native, the godfather of superheroes" is a light novel by the author, Unbridled Beauty Green Plum Wine. It's a derivative doujinshi novel. The general plot of this novel is as follows: Enke had traveled through the Marvel Universe and obtained Compound 5 replacement system! As long as it was a valuable item, it could be exchanged for points to exchange for all kinds of powerful #5 compound! At the beginning of the fusion of Compound No. 5, he had obtained the ability of a native. In order to obtain more valuable items, Enke directly chose to bring Captain America to join the army! Thus, an invincible superman appeared on the battlefield! Smashing a tank with his bare hands! His hot vision swept across everything! It flew across the entire battlefield! All the countries were stunned, and so was the Hydra! How did this monster come out? Captain M: I already said that he and I are both products of the super soldier serum. Why don't I believe it at all? … It was not just the ability of the natives. When Enke showed more of the ability of Compound No. 5, everyone was numb! Tony Stark: What the hell is this Steel Body? I think he's Iron Man, right?" "Teleport with people?" Magneto asked. Realization? This is the god of the mutated humans!" Black Marinated Egg: "Stop talking. The Fu Lian should disband on the spot. We can't beat his Black Robes Public Order Squad!" Enke stood above the Empire State Building and looked down at everything. I'll do whatever I want!" ---------------------------- Marvel Mercenary was a light novel by the author, Wolf Ghost Ink. The general plot of the novel was: Harry accidentally passed through the Marvel team. When he was in danger, the team watched him die in the sea of fire, but he was helpless. After surviving the disaster, he found that he had great strength and defense, and thus became a mercenary who was both good and evil. Kicking Hulk, punching Thor, sitting on the Throne of Slayer! [If you like it, please recommend it. If you don't like it, please don't comment!] ---------------------------- "The Strongest Captain America" was a novel written by the author, I Don't Know Magic. The general plot of this novel was: Shi Di had transmigrated to the Marvel World. However, the difference between this place and the past was that this was the world after Thanos snapped his fingers. The number of superheroes was already on the verge of extinction. The number of villains was constantly increasing. But at this time, Shi Di accidentally got the shield of the dead American team. Congratulations to the host for activating the Captain America System. When you gain the favor of others, you can gain Justice Points. When the enemy's attribute panel exceeded 100%, he would immediately obtain 50% of the enemy's attributes. In the Technology Tree, Justice Points could activate the Shield and Bodywork branches and unlock various skills. The Lottery System allowed one to draw a lottery by spending Justice Points. It was the best choice to get rich overnight. ---------------------------- Marvel: Dark Mimicry was a light novel by Snow Knows Everything, a derivative doujinshi novel. The general plot of the novel was: He had traveled through Marvel and become a "mutant" with the ability to copy. At the same time, he had awakened a strange golden finger. [Professor X and Magneto: Child, the future of the mutants depends on you!] Thunder God: "Old man, don't talk. Let him return the hammer to me first!" Captain America: It's time to show 50 - 50…F * ck? Why couldn't it move! Venom: Hey, Host, I think cumin-flavored Captain America will be very delicious! The ultimate battle. Thanos smiled wickedly and snapped his fingers at Calvin! Pa! What the f * ck? What was going on? Pa, pa, pa… Ps1: Please refer to this book for the timeline! Ps2: The cheat is not the system! Ps3: Description of patients with severe weakness. ---------------------------- Marvel Superheroes was a novel written by the author, Stupid Brother. The general plot of the novel was: He and Captain America were brothers who crossed the river of time. They experienced hardships to become a super soldier, met Professor X, and changed the future together with the professor. He and Iron Man's father were good friends. r Time flies, I live to the age where heroes shine This was a history of growing up in the Marvel movie world! white. Latiz-Become your own hero! ---------------------------- "I earn money by killing monsters in American Manga Entertainment" was a manga novel written by the author, Yen Shisanyue. The general plot of this novel was: Sean was a money-grubber who had transmigrated to the world of American Film and Television and Marvel. There were no DCs. The main characters in the movie had become monsters. What Sean needed to do was to spar with these monsters. If he won, he would drop money and skill books. The timeline and location were all messy, but the plot was real. Some of the plausible ones were original plots that were pieced together. When it came to relationships, the protagonist was a scumbag. It was mainly American Film and Television, with an additional Marvel. Marvel was mainly an adaptation of the Secret Empire. The American team was the villain. The one who saved the world was not the real American team, but the protagonist. Captain America fans, please leave! The main genre of movies were police and gangster horror movies. There would also be some sci-fi stuff and alien abilities. There was no magic, no zombies, no superpowers. The protagonist was just a character between Iron Man, Hulk, and Captain America. Slowly, martial arts, open force, hidden force, and transformed force appeared on the protagonist's body. At the same time, it was also about technology. The combination of martial arts and technology. Using a mortal body to fight against extraterrestrial creatures in the universe... ---------------------------- "Film and Television Begins with the SEALs" was a military-military war novel written by the author, Little Soldier. The general plot of the novel was: He was reborn as a navy soldier and became a top-notch special forces soldier of the Navy SEALs. Patriotic? It didn't exist! Making money was the way to go. Dollar was so fragrant, and there were zero-dollar purchases everywhere. He had to take the opportunity to get more. I'll set a small goal first and earn him 100 billion! [Movies currently available: Seal Team Six, Black Hawk Down, Operation Red Wing, Border Killer, 13 Hours of Crisis, Shocking Rescue, Operation Brave, Fast Chase, Mechanic, Navy SEALs, Tarkov, Life or Death Sniper, Hurricane Rescue…] ---------------------------- "Beautiful Manga: The Ancestor of the Beginning, Destroying the American Team with a Single Punch" was a light novel by the author, Chuyao. The general plot of this novel was: When Sean woke up, he found that he had come to the world of comics and had become the evil personality of the superman. Coincidentally, the outside world began to denounce Superman. Hence, Sean was furious. "A mere mortal dares to provoke a god?" "I'm not Superman. I'm an ancestor. Whoever provokes me will die!" ---------------------------- Marvel's Lucky Star was a light novel written by the author, Black and White Chinese Scholar. The general plot of the novel was: I accidentally came to the M Nation after World War I, but why did an angel fall in front of me? He had thought that he would end his life in World War II, but who was the one who could not be killed? "Fortunately, I can't live to see the messy world behind me…" Jack Lin sighed with relief as he watched Captain America fly away. "We meet again, Roger!" Strange, I'm your senior brother!" "Tony! You've grown up! Me? I'm your godfather!" "Charles, do you want to guess the size?" This was the growth history of a man who could live to the end. ---------------------------- "The Hydra Spy of the American Manga" was a novel written by Squirrel, the author of the novel. The general plot of the novel was: After traveling through the Marvel World and becoming the Hydra spy Grant Ward, he was faced with two choices. S.H.I.E.L.D. or…Hydra? "Long live Hydra!"
One interesting plot idea could be that Captain America and Agent 13 are on a mission to retrieve a powerful and dangerous artifact. Along the way, they face many challenges and have to rely on each other's skills. Agent 13 uses her espionage skills to gather intel, while Captain America uses his combat abilities to fight off enemies.
One plot idea could be Captain America joining the Justice League temporarily. He could bring his military tactics and sense of honor, and have clashes and then reconciliations with Batman over leadership and strategy. For example, when facing a powerful alien invasion, Captain America might advocate for a more direct, all - out attack while Batman prefers a more stealthy, long - term plan.
One plot idea could be that Captain America and Scarlet Witch team up to face a new, powerful villain who has the ability to manipulate time. They have to combine Captain America's combat skills and leadership with Scarlet Witch's reality - warping powers to defeat the foe.
One idea could be a time - travel fanfic where Captain Marvel and Captain America team up in a different era. Maybe they end up in the 1920s and have to deal with a Hydra - like threat that's starting to form early. Another could be a fanfic where they swap powers for a day and have to learn to adapt to each other's abilities. For example, Captain America trying to control Captain Marvel's photon blasts and Captain Marvel having to rely on just her combat skills like Cap usually does.
One plot idea could be that Black Widow and Captain America are on a secret mission together in a war - torn country. They have to rely on each other's skills to infiltrate an enemy base and retrieve a dangerous weapon. Another could be a story set in the past, where they first meet during their training days and form an unlikely friendship that develops over time. Maybe a plot where they are both framed for a crime they didn't commit and have to work together to clear their names while also uncovering a larger conspiracy within S.H.I.E.L.D.
Well, you could write a 'Captain America experiment fanfic' where the experiment was part of a larger, inter - dimensional experiment. Maybe in this fanfic, Captain America's experiment not only changed him physically but also opened a portal to another dimension. And from that dimension, new threats or allies come into play. You could also have a story where the experiment was a test by an ancient civilization that was long forgotten, and as Captain America discovers the truth about the experiment, he has to deal with the implications of this ancient knowledge.
One idea could be a story where they discover the pregnancy during a time of peace after a major battle. They are both overjoyed but also a bit worried about how to balance their superhero duties with starting a family. Steve (Captain America) might be extra protective of Peggy, and they start making plans for a nursery in their home.
Another idea is that there's a villain who can manipulate time and space. He sends Captain America to the Naruto world during a crucial time in Naruto's story, like right before a big battle. Captain America's leadership and battle experience help Naruto and his friends come up with a better strategy. And in the process, they learn from each other's values and fighting styles.
One plot idea could be an OC who is a scientist during World War II and teams up with Captain America. They could work on some top - secret projects together. Another is an OC who is a foreign agent sent to assess Captain America's abilities and ends up becoming his ally. Maybe an OC from the future who travels back in time to help Captain America prevent a major catastrophe that wasn't in the original timeline.