A/N: I do not own any Marvel characters.
After seeing how things played out in Earth-TRN898, I, The Watcher, could not resist glimpsing back into the universe to see what happened next…. Pepper and Shuri were able to convince everyone that Killmonger was the real enemy, and he was exiled from Wakanda. Since no other heirs were left, Shuri became the Black Panther and heir to the throne of Wakanda. But other events, set in motion by the deaths of Tony, Rhodey, and T'Challa, would have far-reaching consequences….
2012: To counter the threat posed by Loki and the Chitauri, Nick Fury still formed the Avengers…but they were a team of five, not six. When Loki's allies attacked the Helicarrier to free him, Iron Man was not around to keep the Helicarrier airborne, and it crashed in the Atlantic Ocean off the coast of Virginia. The crash took Hawkeye's life, leaving only four Avengers as Earth's first line of defense during the Battle of New York. With Iron Man not around to carry the nuke through the wormhole and destroy the Chitauri mothership, Thor did so instead…but didn't make it back through the wormhole before it was shut, and was lost in space.
At the end of the year, when Aldrich Killian kidnapped President Ellis, Captain America and Black Widow were sent to save him. Unfortunately, they didn't arrive in time – Ellis was killed, and in the following battle, Captain America's leg was badly burned by one of the Extremis-powered A.I.M. agents, leaving him with a slight limp for the rest of his life. Vice President Rodriguez succeeded President Ellis, and A.I.M.'s attacks around the U.S. continued. A victim of one of these attacks was none other than Jane Foster.
2013: Because of Jane Foster's death, the Aether was never disturbed during the Convergence. The Dark Elves never discovered it, and the Aether remained hidden for years to come.
2014: During HYDRA's attempt to take over the world with Project Insight, Captain America, Black Widow, and Falcon allied to stop them. Unfortunately, Cap's injury from the battle with A.I.M. kept him from replacing the third Helicarrier's targeting chip in time. In the few seconds the Helicarrier was active, over 10,000 people on the eastern seaboard were killed, including Stephen Strange and, as fate would have it, the man who would one day kill Ben Parker. Because of that, his nephew would never learn the harsh lesson that with great power, there must also come great responsibility.
2015: The four current Avengers – Captain America, Hulk, Black Widow, and Falcon launched an attack on Baron Strucker's HYDRA fortress and took Loki's scepter from him before battling Quicksilver and Scarlet Witch. The twins got away and, searching for a way to take down the Avengers, sought out and allied with Killmonger since he had murdered Tony Stark. The Avengers and Wakandans ultimately allied to defeat them, leading to a massive battle outside Wakanda. The Maximoffs were killed in the battle, and Killmonger was captured and imprisoned in a cell beneath the Pentagon.
2016: When the Avengers were sent to Lagos, Nigeria to stop Crossbones, his suicide bomb killed both him and Captain America, since Scarlet Witch wasn't there to contain the blast. After that, only three Avengers were left – Hulk, Black Widow, and Falcon. People began to believe that the age of superheroes was coming to an end.
2017: In this reality, Spider-Man's conflict with the Vulture led to a far worse version of the battle on the Staten Island Ferry. After webbing up the Chitauri-powered weapon on the Ferry, he swung it at the Vulture, causing a massive explosion that killed the Vulture and also completely destroyed the upper levels of the Ferry. Spider-Man was arrested and imprisoned for murder.
Later in the year, Surtur amassed an army of Asgard's enemies and besieged it. After holding out for a few weeks, Asgard's defenses crumbled and Surtur's army overran it. Everyone on Asgard died, including Odin, Loki, and Frigga, as no ship was present to save any of them. In the explosion that destroyed Asgard, the Tesseract's shell was destroyed, leaving the Space Stone to float adrift in the cosmos.
2018: I hesitated to even look on this year, but my curiosity eventually won out. After destroying Xandar to obtain the Power Stone, Thanos located the Space Stone and collected that too. He then sent his generals to obtain the Time and Mind Stones on Earth, as well as the Reality Stone from its secret location across the cosmos. Thanos himself, meanwhile, ambushed the Guardians of the Galaxy in the Sanctuary II and captured Gamora. Star-Lord and Drax were killed in the battle, while Rocket, Groot, and Mantis managed to get away in the Benatar's escape pod. Thanos took Gamora to Vormir, where he obtained the Soul Stone.
Corvus Glaive led a horde of Outriders to attack the Avengers Compound, where Loki's scepter was being held. The three Avengers were caught off-guard, and before the battle started, Corvus Glaive presented the Avengers with Thor's severed head. He revealed that Thanos had captured Thor since he didn't make it back through the wormhole in time, and murdered the God of Thunder in retribution for the Chitauri mothership being destroyed. The Avengers were hopelessly outpowered; Falcon, Black Widow, and even Hulk were all killed, the latter by Corvus Glaive's weapon. Proxima Midnight, meanwhile, recovered the Reality Stone, but doing so awoke the Dark Elves, who tried to stop her. Her Q-Ship was shot down above Svartalfheim, and Malekith took the Aether from her.
In New York City, Ebony Maw and Cull Obsidian confronted the Ancient One, but Cull Obsidian was killed in the ensuing battle and Ebony Maw was forced to retreat to his rendezvous with Thanos on Titan empty-handed. Upon realizing that Proxima Midnight was absent, Thanos tracked her Q-Ship to Svartalfheim, where he killed Malekith and took the Reality Stone from him. He and his army headed to Earth and attacked New York City again to take the Time Stone, but Rocket, Groot, and Mantis arrived on Earth with the Ravager fleet to battle Thanos. But while the Black Order held them off, Thanos was able to use the power of the five Infinity Stones he had to break the enchantment that bound the Time Stone to its owner. After inserting the Time Stone into the Infinity Gauntlet, he snapped his fingers, disintegrating half of all life, including Groot, Mantis, Stakar, and the Ancient One.
In California, Hank Pym and Hope and Janet van Dyne disintegrated before Ant-Man entered the Quantum Realm. Because he wasn't stuck in there, he never discovered that the Quantum Realm could be used to travel through time. Thanos' actions were never undone.
Three weeks later, Captain Marvel arrived on Earth and headed to Thanos' home on the Garden with Rocket and Nebula, who had escaped the Sanctuary II during the battle in New York. But upon reaching the Garden, they discovered that Thanos had destroyed the Infinity Stones to prevent his actions being undone. Rocket blew off the Mad Titan's head in revenge, but the universe would never be the same.
And so Tony Stark being saved ended in trillions of souls not being…avenged.
A/N: I'm considering doing something like this for other episodes of What If...?, the ones that have more of a cliffhanger ending like the zombies one. Until then, I'd love to receive a review of the story!