It depends on the specific fanfiction. In some stories, Superior Iron Man might be more powerful because he's willing to push the limits of his technology and his morals further. But in others, Iron Man could be more powerful due to his experience and his ability to work well with others.
In the comics, Iron Man did not kill Captain America. Their conflicts and battles were part of the storylines, but not to the extent of one killing the other. The relationship between them was complex but not fatal.
In the comics, Iron Man doesn't end up killing Captain America. Their battles and disputes have various outcomes, but not one that involves a fatal blow from Iron Man.
In the world of fanfiction, the idea of Iron Man killing Captain America can be quite controversial. Ethically, it goes against the typical heroic and friendly relationship they have in the mainstream Marvel universe. However, fanfiction is a space for exploring different scenarios, so while it may seem unethical to some, it can be a creative exploration for others.
A third common theme is sacrifice. Fanfictions may depict situations where either Captain America or Iron Man has to sacrifice something for the greater good or for the sake of their relationship. It could be something as simple as sacrificing personal time to train together or as big as sacrificing a chance at personal glory to save the other.
There is a fanfic named 'Cap and Iron Man: United Front'. In this, they team up against a new and powerful enemy that threatens the whole world. It's full of action scenes and also some heart - to - heart conversations between them that are really well - written.
One interesting fanfiction could be where Captain America and Iron Man have to team up in an alternate universe to fight a new threat that combines their worst enemies' powers. It could explore their relationship in a different setting, highlighting their differences and how they overcome them to save the day.
It's hard to say for sure. Both Iron Man and Captain America have their unique skills and strengths. It would depend on a lot of factors like the situation, their equipment, and strategy.