One possibility is that the story is set in an alternate universe where the relationship between Bucky and Tony is much more hostile from the start. The arc reactor could be a symbol of power that Bucky wants to take away from Tony for his own reasons, like to gain an advantage in a power struggle within the superhero community. So he rips it out, which then sets off a war between different factions of heroes and villains.
In this fanfiction, perhaps there's a big misunderstanding. Bucky has been led to believe that the arc reactor is some sort of key to a greater evil. So, without fully understanding its importance to Tony, he rips it out. This could then lead to a chain of events where Bucky has to face the consequences and try to make amends while Tony is fighting for his life.
It could be Bucky himself if he's under mind control. He'd be the one directly causing harm to Tony by ripping out the arc reactor, so in that sense, he's the antagonist, even if it's not really his fault.
In this fanfiction, Harry could be in a situation where he is magically linked to Tony Stark. Due to this link, he gains access to the concept of the arc reactor. He then tries to recreate it in the wizarding world with the help of Hermione's research skills and Ron's practical knowledge. They face many challenges as the wizarding world doesn't understand this Muggle technology at first. But eventually, they manage to build an arc reactor - like device that has the power to disrupt dark magic, which they use to defeat Voldemort in a completely unexpected way.
Maybe Peter discovers an old, broken Arc Reactor and decides to fix it up. He could use his scientific knowledge to tinker with it and eventually get it working, which then gives him some new powers or abilities.
One possible plotline could be Peter using the arc reactor to enhance his existing abilities. For example, if he has spider - powers, the arc reactor could make them stronger. Another could be Peter having to protect the arc reactor from villains who want to steal it for their own evil purposes.
Maybe he found it in an abandoned Stark Industries facility. It could have been left behind during some chaos and Peter, being the curious and resourceful guy he is, discovered it and decided to study it.
Well, one consequence could be that his life - support system is affected. Since the arc reactor was keeping him alive in some ways, without it, he might face immediate health risks. He could start to experience weakness and his heart might struggle without the power source the arc reactor provided.
In this fanfiction, perhaps Naruto has seen a side of Sakura that goes against his values. For example, if she starts to use underhanded tactics to get what she wants. Naruto, being the person he is, doesn't tolerate such behavior and he confronts her, really tearing into her actions and motives. It could also be related to her treatment of him. Maybe she has been dismissive of Naruto's feelings for her and he finally snaps and gives her a piece of his mind.
In some comic arcs, Iron Man removing the arc reactor is indeed canon. This action might be driven by various factors such as plot twists, character growth, or to introduce new challenges for the hero.
The arc reactor in fanfiction about Tony Stark is a really cool concept. It can be used to show the evolution of Stark's character. At the start, it might be just a technological marvel for powering his suit. But as the story progresses in the fanfic, it could become something more spiritual or emotional for him. It might represent his connection to his past, his father perhaps, and his journey to become a better hero. And the way different authors play with this idea in their fanfictions is really fascinating.
Perhaps it's related to some sort of new power - up or transformation in the fanfiction. Sometimes in fan - made stories, the author likes to create unique and extreme situations for character development. Naruto might think that by removing his eye, he can unlock a hidden power within him. It could also be due to a misunderstanding. He might be tricked into believing that his eye is the source of some great evil that is about to befall the Hidden Leaf Village and so decides to rip it out to save everyone.