4. Too Many Villains
Malekith and Kurse are confirmed as being in this movie and they are both guaranteed to be villains, Loki's presence will always be a risk, even if he's genuinely out to redeem himself in this movie, while the likes of Tyr who is confirmed as being in this movie have also come to blows with Thor in the comics. On top of the fact that there will be armies of generic bad guys (as seen in the trailers) and giant rock warriors (which Thor is seen to destroy with ease in the latest trailer), this movie is running the risk of suffering from a bad guy overload. There's also the chance that the likes of Surtur could be in this movie as the mastermind behind Malekith's evil operation and there has been a rumour that Benicio del Toro's Collector (who will be one of the main villains in next year's Guardians of the Galaxy) is due to make a brief cameo. Marvel need to be careful. Loki is already ahead of Thor in the popularity stakes with audiences - they don't want to allow Thor to be outshone in his own movie by the fact that the villains could be stealing the show again.