A great Ultron OC fanfiction might involve an OC who is a time - traveler. They go back in time to stop Ultron from being created in the first place. Along the way, they interact with the people involved in Ultron's creation, like Tony Stark, and try to change the course of events without disrupting the timeline too much.
First, create your original character (OC). Decide on their personality, abilities, and backstory. For example, if your OC is a hacker, think about why they became a hacker and what their goals are. Then, think about how they will interact with Ultron. Will they be an enemy, an ally, or something in between? After that, plan out the plot. You can start with a simple idea like your OC discovers Ultron's secret lair.
One memorable OC could be a young hacker who manages to infiltrate Ultron's network. This OC uses their hacking skills not only to gather intelligence on Ultron but also to plant viruses that slow him down. Another could be a super - strong OC with a heart of gold. They are often on the front lines in battles against Ultron's drones, smashing them to pieces with their bare hands.
One interesting plotline could be an OC (Original Character) with special powers that can counter Ultron's technology. For example, an OC who can manipulate energy in a way that disrupts Ultron's programming. Another could be an OC who has a past connection to Ultron's creator, Tony Stark, and this connection plays a role in the battle against Ultron. Maybe the OC was an experiment gone wrong in one of Stark's early projects related to artificial intelligence.
Perhaps the OC is a creation of a mad scientist who wants to use Ultron's technology to enhance their own creation. The OC then rebels against the scientist's control and teams up with Ultron for mutual benefit, leading to a series of adventures where they face various challenges together, such as fighting off military forces trying to destroy them.
Vision could be a great character to pair with an Ultron Robot OC. Since Vision was created from Ultron's original plan, there could be a lot of interesting interactions. The OC could either befriend Vision or be in conflict with him, depending on the nature of the OC.
Spider - Man could use his agility. He could quickly dodge Ultron's attacks and find a weak spot in Ultron's armor. Since he's so fast and nimble, he could get in close and plant some sort of disabling device he made with his scientific knowledge.
In some fanfictions, Ultron might team up with one of Spider - Man's villains, like the Green Goblin. They could create a plan to take over New York. Spider - Man would then have to face this powerful alliance. He might seek help from other superheroes he's associated with, like Iron Man or Daredevil, to combat this new threat.
Another way Peter could be of help is with the setting. He could describe in detail how New York City (or wherever the story is set) looks during the Age of Ultron. With his knowledge of the city streets and rooftops, he could make the battle scenes more vivid and realistic.
It can also be frustrating at times. Some fanfictions lack the proper understanding of the movie's lore. They might introduce concepts that don't fit well with the established Marvel Cinematic Universe. But on the positive side, many fanfictions are a labor of love. Authors pour their passion for the movie into their writing, and that can really shine through, especially when they capture the essence of the characters as we know them from the movie.