Thanos is in full battle armor, and is carrying a double-bladed sword.
Tony, Steve, Natasha and Clint step forward into Thanos' direct line of vision. He smirks as they approach him. "Stark, we meet again. I hadn't expected to have to return this planet so soon." He wonders aloud if it was a mistake to let Tony live in the battle of Titan. The Avengers do not reply, and instead prepare themselves for the inevitable battle.Thanos notices this and cuts to the chase. He asks them about the extra Infinity Stone that he sensed. Steve tells him that they weren't able to save the universe, but now they are ready to avenge it.
Thanos laughs at them as the army behind him grows restless. "The Universe is already saved. I have restored its balance. You should all be falling at my feet, worshipping me." At this point, the other Avengers too step into his vision, and Nebula says, "Father, you will never be a god." the sight of Nebula angers Thanos to an unreasonable extent. The army attacks and the Avengers begin to fight. Some of Tony's robots join the fight, trying to assist them. Meanwhile, Iron Man, Captain America, Black Widow and Ronin try to engage the Titan themselves. While they are all able to hold the battle for a while, it is clear that Thanos and his army has the upper hand.
The Mad Titan tells them that he only holds the stones because he wishes to protect them from those who wish ill. The Infinity Stones are retired and he has no plans to use them. However, when Tony lands a blow on him, he changes his mind and tells them that he will use them if he needs to. But just as he pulls himself up and prepares to use the Stones, they are all distracted by the Bifrost that appears right in the middle of the battlefield. Thor, Carol, and Professor Hulk emerge from it. As Thor charges straight for Thanos, Carol and Banner help to deal with the army of Chitauri and Outriders. Thor engages in a one –on-one with the Titan which allows theother Avengers a moment of respite. Thanos manages to knock Stormbreaker away and comes at Thor with his sword, but Hulk quickly steps in and blocks the hit. Thor quickly summons a bolt of lightning and knocks Thanos away, but they suddenly hear Banner scream, in pain.
His right hand is glowing, and as they approach him, they see that Hulk is holding the Power stone. Clenching his jaw, he drops it into the Gauntlet, where it fits perfectly. The Avengers realize that it is possible to extract the Stones from the old Gauntlet and as a result, their whole battle strategy changes. When Thanos realizes his loss, he is filled with blind rage and picking his sword up, he charges at them. By employing a tactic similar to the one on Titan, the Avengers play to their strengths and distract Thanos, while the other members of the team pick the Stones off the Gauntlet.
Tony manages to rip the Time Stone away first, which weakens Thanos further, but he continues to engage in hand to hand combat with whoever engages him. Captain Marvel proves to be most useful against the horde of attacking aliens. Steve Rogers soon manages to get the Reality Stone from Thanos, and put it into Hulk’s gauntlet. Hulk is staying as far as he can fromThanos, while still being accessible to the Avengers. Thor throws Stormbreaker at Thanos, but he uses the Space Stone to deflect it and send it somewhere far away. Enraged, Thor charges, with lightning and plucks the Space Stone away. As the battle progresses, Clint is able to get the Mind Stone, and as Thor, Carol, Tony and Steve hold Thanos down, Natasha picks up the last stone – the Soul Stone. She runs to Banner and places the final stone in place.
As the Gauntlet becomes complete, there is a sudden surge of gamma energy. Professor Hulk falls to his knees, and begins to shake all over from the pain. He briefly attempts to look up and bring his fingers together to snap, but he seems to be losing control. Suddenly, he begins to grow bigger, and when he turns to Natasha, his eyes have lost all sanity – the Hulk was unleashed by the excess gamma radiation. He rips off the Gauntlet, drops it, and heads straight for Thanos. The Hulk wants a rematch.
Meanwhile, Natasha picks up the gauntlet, but doesn’t know what to do. She tries to get it to Thor or Carol. Thanos manages to break out of the Hulk’s grasp when a horde of Outriders attack, and goes straight for Black Widow. She looks stranded, when Steve Rogers steps in between them. As Thanos runs towards him, he stretches his arm out and summons theStormbreaker. Thor soon joins the fight, along with Nebula. Natasha notices Tony approaching from above, and she throws the gauntlet to him. He catches and prepares to fly to Carol. And then, in the air, he pauses, surveying the field below him. He knows what he must do.
He uses nanites to fill the Gauntlet and fit his arm. Then, he drops right in front of where Thanos is fighting Thor, Nebula and Steve. And as Thanos watches, he snaps his fingers.Thanos screams in anguish. Using the opportunity, Nebula stabs him, in the heart, and Thor swoops in and cuts his head right off. As Tony Stark collapses from the power of the Snap, portals open all around him, and all the dusted Avengers return. Peter Parker comes out of one, excited, but his face falls when he sees Stark. He rushes to his father figure, weeping, but Tony just gives him a slow one-armed hug. Pepper also arrives, and he holds her hand as he finally closes his eyes, his mission complete.
The Avengers have a grand funeral for Tony. The Universe has been saved. Families are reunited.But they still need to return the Tesseract that they took, and Steve volunteers. His goodbye to Bucky seems longer than necessary, and he leaves Sam a package with instructions not to open immediately. He steps into the Time Machine and disappears. But when he doesn’t appear after the designated time, Bucky begins to smile.Sam’spackage is revealed to contain the Captain America shield.Thor returns to NewAsgard, a better King than he was before. Banner eventually returned to being Professor Hulk and continues his research for a more permanent solution.
Balance is restored.