Originally Posted by Godzilla2000
It could also be that Thor will have to make a choice of which one he has to choose to save from being overtaken with dark energy, Loki or Jane. I'm sure Thor choosing Jane, a mortal whom he loves over Loki, the brother he professed to love will be the one thing that would drive Loki to ultimately help Surtur and cause Ragnarok because with that much anger inside Loki most likely would want everything Thor cherishes destroyed just to get back at Thor betraying him.
Loki could possibly feel that way, since he feels alienated from his family anyway. Thor could reasonably make the argument that Jane is less able to fend for herself. (To pick a nit, the possession thing we think takes place near the beginning, and Thor and Jane start the movie not (yet) in love.) And as an aside, this dilemma might not even arise. Loki is supposed to be a very powerful sorcerer, so he ought to be able to keep himself from being taken over by dark energy.