Avengers: Endgame was the peak of the Marvel Cinematic Universe so far, bringing together all of this universe’s heroes to stop Thanos and his armies, but it also saw the original Avengers go through major changes, and one of the most surprising ones was Thor’s, who became Fat Thor – but looking back at his history in the MCU, his transformation wasn’t that surprising. For over a decade, the MCU has been bringing a variety of characters from Marvel Comics to the big screen, and among the first heroes to be introduced was the God of Thunder himself, Thor (Chris Hemsworth).
Thor made his MCU debut in 2011 in his first solo movie, simply titled Thor, directed by Kenneth Branagh. Thor returned the following year in The Avengers and later starred in his second solo adventure, Thor: The Dark World. Unfortunately, Thor 2 ended up being one of the weakest MCU movies and established Thor as one of the plainest characters in this universe, which didn’t change much during his appearance in Avengers: Age of Ultron – but his third solo movie, Thor: Ragnarok, made some very necessary changes to him. Under Taika Waititi’s direction, Thor was further developed and given a sense of humor, making his return in Avengers: Infinity War and Avengers: Endgame exciting ones, and allowing him to stay longer with Thor: Love and Thunder.
Thor went through another major change in Avengers: Endgame when he transformed into Fat Thor as a result of the depression he was going through. Five years after the snap that wiped out half of life in the universe, Thor was shown overweight and depressed in New Asgard, where even though he was king, he spent his time locked up in his house, drinking beer and playing video games. Thor’s transformation into Fat Thor came as a surprise to many, but looking back at his history in the MCU, it was foreshadowed from the beginning, with many failures and an egotistical mindset that ultimately led to a major loss of confidence and an inevitable snap within him.
When viewers met the MCU’s Thor, he was the arrogant heir to the throne of Asgard, and it was his ego that led to his exile from Asgard to Midgard. As Odin’s eldest son, Thor was supposed to take the throne of Asgard and was preparing to do so when he let his ego take over and made the impulsive decision of attacking Jotunheim and the Frost Giants after the latter tried to steal the Casket of Ancient Winters from Asgard. Thor did so against Odin’s orders and out of rage as his coronation was ruined and delayed, and as he also put many lives in danger through his actions and thus showed to be unworthy of being king, Odin decided to banish him to Earth and he became unworthy of wielding Mjölnir. This was Thor’s first failure in the MCU and the beginning of a buildup of regret and a gradual loss of confidence.
Avengers: Age of Ultron was the introduction of Wanda (Elizabeth Olsen) and Pietro Maximoff (Aaron Taylor-Johnson), and the former used her powers to mess with the Avengers at a very deep and personal level. Wanda wrapped their minds and gave them illusions that reflected their deepest fears and desires, and Thor, being a god, thought he would be immune to Wanda’s power, saying “take special care, I doubt if humans can keep her at bay. Fortunately, I am mighty…”, and right after that, he found himself in a very discouraging vision. This showed Thor that he isn’t the powerful god he thought, and even he could be subjected to mind-wrapping illusions.
Thor went from attacking one of the Nine Realms out of rage for delaying his coronation and resentment because Odin didn’t let him act as king, to avoiding taking his place on the throne of Asgard, showing his gradual loss of confidence after the above failures. At the end of Thor: The Dark World, Thor renounced his claim to the throne to return to Earth to be with Jane Foster (Natalie Portman), but he kept his promise of protecting the Nine realms (something he also failed at, but more on that later). In Thor: Ragnarok, it was revealed that Thor and Loki (Tom Hiddleston) had an older sister: Hela (Cate Blanchett), and so she was the heir to the throne. When she arrived at the throne room, Hela found Thor sitting in it and told her he would love for someone else to rule, and it couldn’t be her because she was the worst. Thor couldn’t even rule New Asgard properly (though that’s when his transformation into Fat Thor began), and ultimately, he handed the reign to Valkyrie (Tessa Thompson).
Thor’s vision induced by Wanda in Avengers: Age of Ultron included a look at the Infinity Stones, which led him to seek Erik Selvig (Stellan Skarsgård) for help. Thor and Selvig went to the Water of Sight so Thor could revisit his vision/nightmare and decipher it, and concluded that, as the hero between the Nine Realms, it was his duty to research and find the Infinity Stones as some of them had already been involved in major incidents. Unfortunately, this was another failure for Thor as after two years looking for the Stones he didn’t get any, but his dreams of the destruction of Asgard became more recurrent, so his plan changed and he instead went after Surtur as he saw him at the center of all the destruction. Thor ultimately also failed at saving Asgard as the only way to defeat Hela was to unleash Surtur, which in turn meant the destruction of Asgard. To further add to the drama, Thanos and the Black Order attacked the Statesman, the spaceship carrying the Asgardians, killing half of the people there as the other half escaped thanks to Valkyrie, and Thor witnessed this and Loki’s demise at the hands of Thanos.
Thor’s failed attempt to find the Infinity Stones led to Thanos finding them and mounting them on the Infinity Gauntlet so he could bring “balance” to the universe by wiping out half of life in it – and with the above-mentioned massacre at the Statesman and Loki’s death, the conflict between Thor and Thanos got personal. After making Stormbreaker in Nidavellir with the help of Eitri (Peter Dinklage), Rocket Raccoon, and Groot, Thor returned to Earth and joined the Battle of Wakanda, where he fought against Thanos. Thor chose to strike the Mad Titan directly in the chest so he could taunt him, and while he briefly overpowered him, Thanos was still able to snap his fingers, telling the God of Thunder he “should have gone for the head”. After all those past failures, being so close to stopping Thanos and failing was Thor’s breaking point, and while he got his revenge by decapitating him not long after the snap, Thor fell into a deep depression that led to his transformation into Fat Thor.
Although failing to stop Thanos while being so close to it could have been enough reason for Thor to go through a heavy depressive episode, it was actually the last straw after all those past failures that took a toll on his confidence as an Asgardian god, a hero, and a protector of the Nine Realms. Thor will go back to his muscular physique in Thor: Love and Thunder, but it’s to be seen how this new transformation will be addressed, as it goes a lot deeper than just Thor’s physical appearance.