Na série de filmes do Thor,
Loki, disguised as an Asgardian soldier, was left alone with Odin, and when "Odin" next appears in the movie, when Thor spoke to him at the end of the movie to report Loki's apparent death, it is revealed that this "Odin" is actually Loki in disguise. It suggests a possibility that Loki may have assassinated or at least held Odin captive and hidden to take his place in secret. The former is very possible, while the latter seems much more difficult to pull off considering Odin's powers and what little Loki seem to have on hand to use against Odin even despite the element of surprise.
Então o que realmente aconteceu?
[Director] Alan Taylor was a little more blunt in his answer, confirming that Odin is definitely dead and that it was a specific decision they made in the process of developing the film:
"That was a big twist. It took us a while to realize that we were actually going to kill him. And then it took us a while to realize that we were going to do that at the end."