Well, if Tony wasn't there to assist, the balance of power would have shifted greatly in Thanos' favor. It's likely that the heroes would have faced more losses and the fate of the universe would have hung in the balance in a much more uncertain way.
If Tony didn't die, the story would be drastically different. For one, the Avengers would still have his leadership and resources. His presence would change the dynamic during the post - Endgame events. They wouldn't be mourning his loss, but instead, be planning new strategies with him at the helm.
In a fanfiction where Tony didn't die, he could continue to be a mentor to the new generation of Avengers. He would use his genius intellect to develop even more advanced technology to protect the Earth. Maybe he'd finally have the time to focus on his family life with Pepper and their daughter, while still being involved in superhero affairs on a more strategic level.
Well, if Roman Reigns didn't get sick, he could have maintained his momentum and faced different opponents in more epic matches. His storyline might have taken a completely different turn, leading to unexpected alliances and rivalries.
Well, it could have led to a very different fate for him. Maybe he would have played a more prominent role in the political affairs of the Targaryen family.
If Steve had come clean to Tony, it's likely that they would have had a deeper level of trust. This could have impacted the course of events in the fanfiction, allowing them to overcome challenges more effectively and creating a more harmonious narrative.
It would likely be a very different place. Without Tony Stark's genius and charisma, many of the technological advancements and heroic deeds he's known for wouldn't have happened.
Well, if Edward didn't leave, there could have been more opportunities for character growth and exploration of their connection. Maybe they would have faced new challenges together instead of separately.
Endgame deviated from the comics in several key plot points. For example, some character arcs and events were significantly different.
A common plot involves Tony being resurrected by some kind of magic or advanced technology. For example, the Wakandans could have a secret method of bringing the dead back to life that they use on Tony. Or, in the Quantum Realm, there could be a phenomenon that reverses death, and Scott Lang discovers it and uses it to save Tony. Also, some fanfictions have Tony's soul being saved by a powerful being like the Sorcerer Supreme and then being put back into his body.
One way could be through some kind of time - related magic. Maybe Doctor Strange finds a way to manipulate time even more precisely than he did in the movie. He could create a special time loop that spares Tony's life while still achieving victory over Thanos. Another possibility is that Pepper, using her own intellect and some Stark technology she's been secretly working on, manages to reverse the effects of the Infinity Stones on Tony at the last moment.