Yes, there are likely fanfictions out there where Tony kills Thanos. The Marvel universe has a huge fan base, and fans often create alternative storylines. Some might explore this scenario to give a different take on the Infinity War and Endgame stories.
Well, it's not super common but it does exist. There are different reasons for this kind of plot. Maybe the writer wants to explore the consequences of a breakdown in their relationship. They had their differences in the movies, like in 'Civil War', and some fanfic writers take it to an extreme by having Tony kill Steve to show how far things can go wrong when they can't resolve their issues.
Yes, there might be such a fanfiction out there. Fanfiction often explores dark and alternative storylines. However, it can be quite a controversial and dark concept as Tony and Peter have a mentor - mentee relationship in the mainstream Marvel stories.
One possible motive could be that the souk stone has some sort of power that Tony is desperate to obtain. Maybe it can grant him ultimate power or fulfill a long - held desire, and Peter is just an obstacle in his way.
Some writers might want to explore dark and extreme scenarios. It's a way to break the norms of the usual heroic storylines. They may be interested in seeing how the characters and the Marvel universe would react to such a tragic event.
One possible plot could be a misunderstanding that leads Steve to believe Tony has done something extremely harmful to the team or innocents. For example, if there was false evidence suggesting Tony was secretly working with an enemy. Another plot might involve a moral disagreement that gets out of hand. Maybe they have different views on how to handle a new threat and Steve, in a moment of extreme passion, makes a terrible mistake.
In a 'Tony kills Thanos' fanfiction, the plot could start with Tony being haunted by his previous failures against Thanos. He decides to go on a solo mission to study Thanos more closely. He discovers a way to disrupt Thanos' connection to the Infinity Stones. With this knowledge, he devises a plan. He lures Thanos into a trap where he has set up a device that can nullify the power of the Stones. Then, in a tense battle, Tony uses his own advanced technology and combat skills to fight Thanos without the Stones' advantage and finally manages to kill him. This could be a story of redemption for Tony, showing his determination and ingenuity in the face of seemingly insurmountable odds.
One common theme could be sacrifice. In the main MCU storyline, Tony Stark sacrifices himself to save the universe. Fanfiction might expand on this self - sacrifice, exploring his inner thoughts and emotions before making such a drastic decision. Maybe he feels it's the only way to atone for past mistakes or protect his loved ones in a more permanent way.
One reason could be to explore the extreme consequences of their ideological differences. In the official story, they had disputes over things like the Sokovia Accords. In fanfiction, this could be pushed to the limit, leading to Tony taking Steve's life.
Some fans would be extremely shocked and disappointed. Steve and Tony are two beloved characters, and their relationship is complex and interesting. Killing one of them off in such a way would be a huge departure from what many expect.