Yes, there are likely some out there in the vast world of fanfiction. Fanfiction writers often come up with unique and unexpected crossovers like this. However, the quality and popularity can vary greatly.
Yes, there are some out there. You can start by looking on popular fanfiction websites like Archive of Our Own or FanFiction.net. Just search for the specific tag'superman kills batman' and you'll find a variety of stories. However, the quality can vary greatly from one to another.
In this fanfiction, Superman might use his super strength to physically stop Batman from harming Robin. He could also use his heat vision to create barriers or distractions.
One possible reason could be mind control. Maybe some villain has taken over Superman's mind and made him do it. Another reason might be a fundamental difference in their ideologies that has escalated to the point of no return.
One common theme is the corruption of power. Maybe Superman's power has gone to his head, and Batman sees the need to stop him at all costs. Another could be a mind - control scenario where Superman is being controlled by an outside force and Batman has no other option.
A 'Naruto kills Superman' fanfiction could be a complex and exciting read. Naruto would have to find a way to counter Superman's strength, flight, and heat vision. Maybe he would team up with some of his ninja comrades at first to study Superman's abilities. He could use his ninjutsu to create illusions and misdirect Superman. Once he figures out a strategy, perhaps using a combination of his most powerful jutsu like the Tailed Beast Bomb. It would also depend on the rules set in the fanfiction world, such as if there are any limitations on Superman's powers or if Naruto has any new abilities or enhancements. The story could also explore the moral implications of Naruto killing Superman, which could add depth to the narrative.
A common theme is the corruption of the hero. Batman is known for his strict moral code, so when he kills Robin, it shows a breakdown of that code. Another theme could be the exploration of the consequences of power. Batman has a great deal of power and influence, and killing Robin could be a way to show what happens when that power is misused.
One possible plot could be that Superman and Robin team up to stop a powerful villain who is causing chaos in Gotham City. Maybe the villain has some kryptonite - based weaponry which makes it tough for Superman, and Robin uses his detective skills to figure out how to disable it. Then they combine their powers, Superman's super strength and flight with Robin's martial arts and acrobatics, to defeat the bad guy.
There are indeed some 'batman kills superman fanfic' out there. In some, the writer might be exploring a darker take on the DC universe. It could be due to a breakdown in the relationship between the two heroes, or some external threat that forces Batman's hand. But you have to search through a lot of not - so - great ones to find the gems.