Odin Secretly Hinted At Ragnarok's Hela Twist In 2011's Thor Movie
Hela was never mentioned before her appearance in Thor: Ragnarok, but her arrival might have been set up in Odin's speech in the first Thor movie.
The Marvel Cinematic Universe is full of moments of foreshadowing and hints that pay off years later, and all of this happened in the first Thor movie, in which Odin secretly hinted at Thor: Ragnarok’s Hela twist. The MCU’s Phase 1 was the audience’s introduction to the original Avengers team, with most of them getting solo adventures, among those Thor (Chris Hemsworth). The Asgardian prince made his debut in Kenneth Branagh’s Thor in 2011, and he has come a long way from his days as the son of Odin who was banished to Earth.
Thor also introduced the God of Thunder’s family – his father Odin (Anthony Hopkins), his mother Frigga (Rene Russo), and his adopted brother Loki (Tom Hiddleston) – though not all of them got much screen time. After joining the Avengers the following year, Thor returned in Thor: The Dark World, one of the weakest MCU movies, which even though introduced another Infinity Stone thanks to the Aether, didn’t do much for Thor’s development. After another mission with the Avengers, Thor returned in Thor: Ragnarok and got a major upgrade as he was finally given a personality and the character development he needed, but it also made some big changes to his family's backstory.
Thor: Ragnarok caught up with Thor after he left Earth at the end of Avengers: Age of Ultron and revealed that Thor isn’t Odin’s only child. As it turns out, Odin’s firstborn was Hela (Cate Blanchett), the goddess of death, who had been imprisoned in Hel by Odin for many, many years. Odin’s death broke Hela free, and she was ready to continue her plans of ruling Asgard and creating an Asgardian Empire. Hela had never been mentioned in the MCU before Thor: Ragnarok, and the explanation given in the movie was that Odin wiped all record of her from history – however, a subtle detail in the Allfather’s speech during Thor’s coronation in the God of Thunder’s debut movie set up the arrival of Hela.
A Reddit user pointed out a subtle but important detail in Odin’s speech during Thor’s coronation scene in his debut movie that set up the twist of Hela being Odin’s eldest daughter in the MCU. In the scene, Odin says “Thor Odinson, my heir. My firstborn”, with his voice cracking when saying “firstborn” and the scene immediately cuts to Frigga, who looks away. Years later, Hela was revealed to be Odin’s firstborn, who served as his personal executioner and commander of the Asgardian army. Hela and Odin embarked on a bloody conquest, bringing all of the Nine Realms into Asgard's power, but Hela’s ambition was too dangerous, leading to her banishment to Hel. However, it’s highly possible that that moment in Odin’s speech and Frigga’s reaction was more towards Odin’s words implying Thor is his only son when there was also Loki, who was present at the ceremony.
However, Marvel has left hints and moments of foreshadowing in its movies that pay off years later (though most of the time with some timeline issues), and others have been retroactively confirmed to be what fans theorized, as happened with Peter Parker being the kid in Iron Man 2 dressed as the title hero. This could happen with Odin’s subtle Hela hint in Thor, which would help with the issue of Hela not ever being mentioned before Thor: Ragnarok and suddenly appearing for one movie only.