In the Marvel Cinematic Universe (MCU), Thor first encountered Thanos in the 2012 film “The Avengers,” in which the Mad Titan was revealed to be the true mastermind behind the Chitauri invasion of New York City. However, it wasn’t until the events of “Avengers: Infinity War” and “Avengers: Endgame” that Thor and Thanos had their final showdown.
In “Infinity War,” Thanos is on a quest to collect all six Infinity Stones, powerful artifacts that, when combined, grant the wielder god-like powers. Thor, still grieving the loss of his brother Loki and the destruction of his home world Asgard, joins forces with the Guardians of the Galaxy and other Avengers to stop Thanos from achieving his goal.
The heroes are ultimately unsuccessful, as Thanos manages to collect all six stones and snap his fingers, wiping out half of all life in the universe, including many of the heroes themselves. Thor, who had been tasked with acquiring a weapon capable of killing Thanos, arrives too late to stop the snap and is left devastated by the loss of his friends and loved ones.
In “Endgame,” the remaining Avengers come up with a plan to travel back in time and collect the Infinity Stones before Thanos can get his hands on them. Thor, who has been living in self-imposed exile and has let himself go physically and mentally, joins the mission, hoping to make amends for his failure in the previous film.
After successfully collecting the stones, the Avengers create a new gauntlet to use them against Thanos, who has arrived from the past with his own army to stop them. In the ensuing battle, Thor wields Stormbreaker, the weapon he had acquired in “Infinity War,” and fights against Thanos once again.
Thor initially gains the upper hand, using his lightning powers and the axe’s ability to summon the Bifrost to teleport around the battlefield and strike at Thanos from different angles. However, he is ultimately distracted by the arrival of Thanos’ army, and Thanos manages to land a critical blow on Thor with his double-edged sword.
Just as Thanos is about to deliver the killing blow, Thor’s hammer Mjolnir flies into the scene and hits Thanos in the back. The hammer then returns to its rightful owner, revealing that Thor is still worthy of wielding it despite his recent struggles.
The camera then cuts to reveal that Captain America, who had traveled back in time to return the Infinity Stones to their proper places, is the one holding Mjolnir. He had apparently picked it up during his time in the past and used it to assist Thor in the final battle.
With the help of Captain America, Iron Man, and other heroes, Thor is able to hold off Thanos and his army long enough for Tony Stark to snap his fingers and eradicate them all. However, the cost is high, as Tony sacrifices his own life to use the power of the stones.
In the aftermath of the battle, Thor returns to Asgard, where he has a heartfelt conversation with his mother Frigga. She reminds him that he is still a hero and that it’s okay to not be perfect all the time. Inspired by her words, Thor decides to leave New Asgard in the capable hands of his friend Valkyrie and join the Guardians of the Galaxy on their next adventure.
In conclusion, while Thor did not technically kill Thanos in the MCU, he played a pivotal role in the final battle against the Mad Titan in “Endgame.” With the help of his friends and his trusty weapons Stormbreaker and Mjolnir, he was able to hold off Thanos long enough for the other heroes to save the day.