In Avengers: Endgame, the TVA likely would have taken Thanos out themselves if Iron Man failed to collect the infinity stones. Iron Man using the gauntlet and ultimately sacrificing himself is arguably Endgame's biggest moment. It comes after a cue from Doctor Strange that out of the 14,000,605 outcomes, Iron Man's death would create the one instance where the Avengers actually won the day, therefore saving the universe from another Thanos snap. This happens at the very last minute, as all of the stones float from the infinity gauntlet to the nano gauntlet, at which point Tony Stark says "I am Iron Man," snapping his fingers and becoming the universe's hero, unlike any other before him. This concludes Marvel's Phase 3 in a tight, final, and rightful ending to the saga.
But what if Iron Man hadn't been able to take the infinity stones from Thanos? In short, Thanos would have won. What becomes of the villain after that, and who would have the power to stop him? All the Avengers and every superhero on earth and elsewhere will have been erased.
One Reddit theory posits that the answer to this question is simply that the TVA would prune or reset Earth-616. Keep in mind that Thanos would have snapped all life out of existence in that world, not just half. The second Thanos that uses Pym particles to go back in time realizes that the universe will not accept being "balanced" and that he would have created an entirely new universe of his own. This is a nexus event that would have made that universe stray from the sacred timeline. Since the TVA is tasked with protecting that timeline above all else, they would have no choice but to interfere.
How Would The TVA Kill Thanos?
But how would the TVA defeat Thanos? Easily. For one, they have time sticks that can erase any living beings. The fight would end rather quickly, as Thanos would be fairly easy to track down. Once in the TVA, Thanos's powers and strength would be nullified because infinity stones are as useful in the TVA's headquarters as paperweights, as shown in one memorable Loki scene. So, either the TVA would have to sneak up on Thanos to bring him to justice and reset the timeline or follow through with the more drastic move of pruning Earth-616.
While this may seem extreme or impossible, it's worth remembering that the TVA is run by Kang the Conqueror. In the comics, Kang once rapidly aged Thanos down to a skeleton in a matter of seconds, so the TVA definitely has the guns it needs to solve even the biggest problems. The existence of the TVA, in this case, is comforting and convenient for anyone trying to stop an all-powerful Thanos. Even with nobody left to help the universe, the TVA would intervene, changing the course of history to prevent that nexus event from happening in Avengers: Endgame. If so, Earth-616 would be saved not because of any idealistic or logical reason but merely to preserve the sacred timeline.
