Loki's imprisonment is this fascinating turning point in Thor's arc that reshapes their dynamic completely. Before, Thor saw Loki as this mischievous but ultimately redeemable brother—someone whose schemes could be chalked up to childhood rivalry. But after the Battle of New York and Loki's crimes on Earth, Thor's forced to confront the darker truth: his brother is a genuine threat. There's this heartbreaking scene in 'Thor: The Dark World' where Thor visits Loki in the dungeons, and you can see the conflict in his eyes—love for family warring with duty as a protector of Asgard. It's not just about physical imprisonment; Loki's captivity becomes a psychological weight for Thor, making him question Odin's leadership, Asgard's justice system, and even his own naivety. The later films, especially 'Thor: Ragnarok', show how this tension evolves into a bittersweet alliance when Hela threatens Asgard. Thor's journey from blind optimism to pragmatic hope is deeply tied to how he processes Loki's betrayals and their shared history.
What really gets me is how Loki's imprisonment mirrors Thor's own growth. Thor starts as this brash warrior who'd rather smash problems than talk them out, but Loki's schemes force him to think strategically, to negotiate, to lead. By 'Avengers: Infinity War', Thor's matured enough to see through Loki's final trick (that fake surrender)—but he's also vulnerable enough to grieve genuinely when Loki dies. It's messy, deeply human storytelling that elevates both characters beyond typical hero/villain tropes.