In the spring of 2018, audiences were shocked upon the release of Avengers: Infinity War when the villainous Thanos snapped his fingers, using the Infinity Gauntlet to erase half of all life in the universe, including several fan-favorite Avengers. For the very first time, the mighty Avengers had suffered their first ignoble loss.
Despite the eventual reversal of Thanos's snap in Avengers: Endgame, many fans have spent the last several years wondering how the original battle with the Mad Titan could have been won. In fact, there are plenty of poor decisions made by Earth's Mightiest Heroes, that, had a different choice been made, could have altered the fate of the universe.
Abandoning Ultron
When Tony Stark first began the Ultron project, he saw it as a potential "suit of armor around the world," something that could protect Earth from the threats that the Avengers couldn't surmount. However, Ultron's programming went haywire, leading the AI to attempt world destruction, with the Avengers only barely managing to avoid the extinction of all humanity.
Though Tony and the other Avengers understandably abandoned Ultron after the Sokovia Incident, the fact remains that, had the idea been perfected, it might have made all the difference in the battle against Thanos. Had a functional Ultron unit been in place when Thanos attacked, perhaps the battle could have been won before the Mad Titan even stepped foot on Earth's soil.
Preserving The Time Stone
At the beginning of Infinity War, Tony Stark, Doctor Strange, Bruce Banner, and Wong unite at the Sanctum Sanctorum to plan their defense against Thanos's coming attack. Despite Tony's suggestions otherwise, Strange and Wong refused to destroy the Time Stone in anticipation of Thanos's coming. This stubbornness would only result in Strange losing the Time Stone anyway, one of the worst events in Doctor Strange's life.
The Time Stone proved to be one of the more crucial of the Infinity Stones on Thanos's quest. Not only was it necessary to complete the Gauntlet, but it was also powerful enough to reconstruct the Mind Stone after Wanda Maximoff destroyed it. Had the Time Stone been destroyed at an earlier date, it would have been impossible for Thanos to have completed the Gauntlet.
Ignoring Wanda's Potential
Wanda Maximoff spent much of Infinity War by Vision's side, trying to keep him safe from Thanos's Black Order, which sought after the Mind Stone in his head. It wasn't until mid-way through the Battle of Wakanda that Wanda truly joined the fray, but, by then, it was already too late to stop Thanos's forces.
Since the battle with Thanos, Wanda has consistently proved herself to be one of the most powerful Avengers ever, with abilities that even she doesn't fully understand. The Avengers would have done well to put the Scarlet Witch to use earlier, perhaps changing the course of the battle. In fact, ignoring Wanda's true potential may prove to be a fatal mistake as she joins Doctor Strange in Multiverse of Madness, perhaps as its true villain.
Not Using The Portals
The Sorcerers Supreme employ the energies of the universe to create mystical portals from place to place using their sling rings. These portals have proven invaluable in the midst of battles, especially the Battle of Earth, wherein the resurrected Avengers were able to come to their compatriots' aid against Thanos's armies.
Though Strange and the other sorcerers certainly make use of their portals, theirs is a power that has yet to realize its full potential. These portals could be used to wipe armies off the battlefield, chop off problematic limbs hosting powerful Gauntlets, or escape harm unscathed. Nevertheless, portals tend to be used as nothing more than a means of transportation.
Taking The Fight To Thanos
After boarding Ebony Maw's Q-Ship, Iron Man, Doctor Strange, and Spider-Man elect to travel to Thanos's homeworld of Titan in an effort to take the fight to him rather than await his attack on Earth. This assault did lead to their alliance with the Guardians of the Galaxy but ultimately resulted in a colossal failure.
Despite their valiant efforts, the Avengers' attack on Titan wasn't enough to stop Thanos's quest for the Infinity Stones. In the end, their strategy proved half-baked and unprofitable. Had they taken the time to strategize and prepare for Thanos's arrival, perhaps the inevitable battle would have gone a different way.
Refusing To Trade Lives
When it becomes apparent that Vision's Mind Stone is being targetted by Thanos and the Black Order, the Avengers float the idea of having Wanda destroy it. Steve Rogers immediately shuts down the idea, proclaiming that they "don't trade lives."
Steve's assertion, though honorable, would only spell doom for the universe. Wanda would eventually be forced to execute this nixed plan, only, at that point, it was already too late to stop Thanos, who already possessed the Time Stone, which reversed her actions.
Forgetting About Fury
Throughout all the events of Infinity War, not one of the Avengers ever suggests attempting to track down Nick Fury, the former SHIELD director that brought the team together in the first place. It is only during the film's post-credits scene that Fury shows up, where he is snapped out of existence just after activating his signal to Captain Marvel.
Had the Avengers reached out to Fury sooner, he may have come to the conclusion that Thanos was a threat large enough to warrant calling upon Carol Danvers to return to Earth. With Captain Marvel on their team, the Avengers would have stood a much better chance against stopping Thanos the first time around.
The Runes Of Kauf-Kaul
No Way Home is filled with implications for Spider-Man's future, as well as the larger MCU, but one of the film's aspects has much larger implications than some might initially realize. The Runes of Kauf-Kaul are a mystic power source capable of erasing memory on a small or large scale, including altering reality altogether to do so.
With these Runes in Doctor Strange's arsenal, it stands to reason that it was possible all along for the Avengers to erase Thanos's memory of his crusade to destroy half of all life. The Mad Titan would have been essentially powerless against such a powerful ancient spell, and the world might have been spared his wrath.
Not Going For The Head
After Thanos completed the Infinity Gauntlet, Thor became the universe's last chance at salvation, lodging his new ax, Stormbreaker, into the chest of the Mad Titan. However, his efforts weren't enough to stop him, as Thanos managed to snap his fingers, erasing half of all life in the universe, but not before taunting the god of thunder, telling him that he "should have gone for the head."
This mistake proved to be one of the worst things to ever happen to Thor, and by extension, the rest of the world, leading directly to the Decimation that left the universe reeling for five years. There is no doubt that Thor spent many sleepless nights pondering how the world might have been different had he aimed just a bit higher.
Fighting Divided
Though it didn't come to fruition until the end of Infinity War, the Avengers had already lost the battle with Thanos years earlier. During the events of Civil War, the superhero team was torn in half, with Captain America on one side and Iron Man on the other.
By the time Thanos arrived, the Avengers were fractured, both in numbers and in power. The team divided had no chance of stopping the Mad Titan, and the universe was forced to pay the price. Thankfully for all life in the universe, five years later, the Avengers were able to reunite to undo all that Thanos had wrought.