Well, the plot could involve the OC being reborn with some special powers. Maybe they're reborn as an Asgardian but with a unique twist. They could then interact with the existing MCU characters like Thor or Loki, and get involved in their adventures, perhaps helping to stop a new threat to Asgard or even all of the Nine Realms.
Another possibility could be an original antagonist created specifically for the fanfiction. For example, a powerful sorcerer from a hidden dimension who sees the OC's rebirth as a disruption to the natural order of the MCU universe. This sorcerer could try to eliminate the OC and use their power for their own dark purposes. They might be able to manipulate magic in ways that even Doctor Strange hasn't seen before, making them a formidable foe.
One idea could be creating a male OC who is a brilliant scientist from a small town. He discovers a new form of energy that attracts the attention of Tony Stark. Another could be a male OC with super speed who has to hide his powers until he's forced to use them to save a city. Maybe a male OC who is an alien prince stranded on Earth and has to learn about human culture while also trying to find a way back home.
One popular one could be 'The New Avenger in the Harem'. It features an original character who has to navigate relationships within the MCU world. Another is 'Harem of Heroes' where the OC gets involved with multiple MCU heroes in an interesting way. There's also 'OC's Harem Adventure in the MCU' which has a unique plot of the OC's journey through the MCU with a harem aspect.
First, define your male OC. Decide on his appearance, his powers or skills, and his personality. For example, if he's a tech - genius, think about what kind of tech he specializes in. Then, figure out how he fits into the MCU. Is he a hero, a villain, or something in between? Next, come up with a plot. It could be something like he discovers a hidden threat to the world and has to team up with the Avengers to stop it.
First, create a well - thought - out original character (OC). Decide on their personality, backstory, and powers if any. Then, choose which MCU characters will be part of the harem. Next, come up with a plot that makes sense for the OC to interact with these characters in a harem - like way. For example, it could be a mission - based plot where they all have to work together.
An interesting MCU OC fanfic idea could be an OC who is a journalist. They are always on the hunt for the next big story about the superheroes. This could lead them into all sorts of dangerous situations as they try to get exclusive interviews or expose secrets. Another could be an OC who is a mutant in the MCU (even though mutants are not as prominent yet). This OC would have to deal with being different and feared, while also trying to use their powers for good. And a third idea is an OC who is a reformed villain. They were once on the wrong side but now want to make amends and help the heroes in their fight.
First, focus on their initial reaction to being reborn as an Uchiha. Are they excited, scared, or confused? This will set the tone for their character development. For example, if they are excited, they might be more eager to explore their new powers and the Uchiha heritage right away.
The OC would also face challenges. They would have to adapt to the strict ninja training, the hierarchical system in the village, and deal with the various clans. They might also encounter discrimination if their abilities were too different or if they were not from a well - known clan.
First, create your OC. Decide on their appearance, personality, backstory, and powers if they have any. For example, if your OC is a super - powered being, think about how they got their powers. Then, figure out where they fit into the MCU. Are they a new hero in New York? Or maybe they're from another planet. Next, come up with a basic plot. It could be something like your OC teams up with the Avengers to stop a new threat. And finally, just start writing. Don't worry too much about getting it perfect at first.