In an alternate ending, Iron Man could have convinced Thanos of the futility of his plan. Tony Stark is a very persuasive character. He might have been able to show Thanos that balance doesn't mean wiping out half of all life. He could have presented alternative solutions to overpopulation or resource scarcity on Thanos' home planet, thus averting the snap.
One alternate ending could have been that Doctor Strange saw a different future where all the heroes didn't have to sacrifice so much. Maybe he found a way to defeat Thanos without half of the universe being dusted. For example, he could have used the Time Stone in a more creative way to trap Thanos in a time loop or something similar.
Perhaps in an alternate ending of Infinity War, the Avengers managed to steal all the Infinity Stones from Thanos before he could use them. Captain America could have led a stealth mission, with Black Widow and Hawkeye's help, to infiltrate Thanos' lair. Once they got the stones, they could have either destroyed them or used their combined power to reverse the damage already done to the universe.
One possible alternate ending could be that Doctor Strange actually manages to defeat Thanos using his magic before he can snap his fingers. Strange could have found a way to trap Thanos in a time loop or a different dimension, thus preventing the mass destruction that occurred in the original ending.
In fanfiction, Loki and Thor could have formed an alliance with other unexpected characters during Infinity War. Maybe they would team up with the Guardians of the Galaxy in a different way. Loki could have used his knowledge of the cosmos and his ability to blend in to gather more information about Thanos' plans. Thor could have shared his Asgardian battle strategies with Star - Lord and the others. This would have led to a completely different dynamic in the fight against Thanos, perhaps even resulting in a victory that didn't happen in the movie.
One possible scenario could be that Doctor Strange saw a different future where they managed to stop Thanos before he got all the Infinity Stones. So, the Avengers might have worked together more effectively from the start. For example, they could have sent a team to intercept Thanos on his way to collect the stones on different planets.
A really interesting scenario could be where Thor aimed better when he had the chance to kill Thanos. He could have ended the whole threat right there. If he had struck Thanos in the head instead of the chest, the events of the snap would never have occurred, and the universe would have been saved from that mass destruction.
One possibility could be that they find a way to defeat Thanos together in a more strategic way. Maybe Gamora uses her knowledge of Thanos and his weaknesses to help Peter plan an ambush. Since Peter is known for his quick thinking and Gamora is a fierce warrior, their combined skills could be a powerful force.
If in the fanfiction's alternate ending, Thanos is defeated early, characters like Black Widow and Vision might not have to sacrifice themselves. Their relationships with other characters would continue to grow and develop in a positive way. For example, Vision could further explore his relationship with Wanda. Also, Tony Stark might not be as traumatized, and his relationship with Pepper could progress more smoothly without the weight of the snap on his shoulders.
One possibility could be that Natasha's pregnancy added a new layer of vulnerability. It might have made her more cautious in battles, changing the dynamics of the Avengers' fight. For example, she could have been more hesitant to take on high - risk missions, leading to different strategic decisions within the team.
In an alternate history novel where Lincoln lived, international relations could have been different too. His presence might have influenced how the United States was perceived abroad. Maybe the country would have been more involved in international diplomacy under his continued leadership. Also, his economic policies could have further developed the nation's industries in a different direction, as he had ideas about infrastructure and economic growth that might have been fully realized if he had lived.
One possible alternate ending could be that Iron Man and Captain America come to a truce much earlier. They realize that the real enemy is the outside force that has been manipulating them all along. So, instead of fighting each other, they join forces and expose the true villain, leading to a united Avengers once again.
Doctor Strange could be the key character. Since he had the ability to see different futures, he might have found a way to change the outcome more drastically. For instance, he could have used his magic to trap Thanos in a time - loop or some other magical prison, preventing him from getting any of the stones.