Odin Was Secretly Holding Back Thor’s Power - Theory Explained

screenrant.com:

Thor (Chris Hemsworth) began displaying his true powers of controlling lightning and thunder in 2017's Thor: Ragnarok after the death of Odin (Sir Anthony Hopkins), suggesting that Thor's powers were secretly being held back by Odin. Throughout the MCU to date, Thor has consistently ranked among the franchise's most powerful characters, famously claiming to be the "strongest Avenger" on several occasions. However, it is only after Odin's passing that his full force is unleashed, suggesting a connection.

Thor: Ragnarok featured the return of Thor's villainous sister, Hela (Cate Blanchett), who sought to rule Asgard and the Nine Realms through war and bloodshed. The climax of the film fulfilled the disastrous titular prophecy when Surtur (Clancy Brown) destroyed Asgard and Hela with it. At various points throughout the film, Thor exhibits powers he has never before used in the MCU. He only reaches his full potential, however, after Odin reveals to him that his hammer, Mjolnir, was only a tool meant to help Thor control his powers and that he does not need it to defeat Hela. Thor rightfully earns his godly status after this reveal, by single-handedly overpowering Hela and her undead army. This begs the question as to why did Thor not use these powers against Loki, Malekith, and Ultron earlier in the MCU.

Related: How Powerful Thor Really Is In Each MCU Movie

The most popular answer to this question is that Odin was using his power as the Allfather to dampen Thor's abilities, the same way he forced Hela to stay trapped in her prison for centuries. This would explain why Thor only began to use those abilities after Odin's death, and why he never used them in previous battles, even when the Avengers were on the brink of defeat