The biggest stand-out star from the Thor franchise has (surprisingly) been Loki. Tom Hiddleston is such a fan favorite that he was given center stage at Marvel's Comic-Con presentation this year. So it's only right that the very first clip from Thor 2 be all Loki, Loki, Loki.
In this first ever clip from Thor: The Dark World has both Thor and Loki looking for vengeance. Whatever could hae happened? I think we know.