With Thor 2 on the docket, its now up to the screenwriters to decide who will be butting heads with the Mighty Avenger. That doesn't mean us nerds can't take a crack at it first. Here, the Schemer provides, for your enjoyment or lack thereof, several options the Marvel folks have in the way of villainy for Thor 2.
As I do not believe they will try to have Thor deal with two primary foes (one in Asgard and one on Midgard), there are really two directions to go. The first is the villains and creatures of the Nine Realms, the second is to select a villain of Earth. And of course it is possible that both Asgard and Earth will be involved. So first, the villains of Earth!
#1) The Grey Gargoyle: A French chemist who, thanks to an experiment gone wrong, can turn himself into living stone and trap others in a stony state for hours. He has battled against nearly every Marvel super hero, including Captain America, Iron Man, Hulk, and Thor.
#2) The Wrecking Crew: I'll be honest, I'm not too keen on seeing a group of construction workers gone wrong, and it would capture the cheesy prize of 2013. Sure they get their powers from an Asgardian, but its courtesy of an enchanted crowbar...
#3) Absorbing Man: Loki turns Crusher Creel into a superhuman who can turn his body into anything he touches. Although it may make for a fun battle, Creel doesn't quite strike me as the 'main villain' type. Maybe as part of a Loki-recruited gang of villains though...
#4) Mr. Hyde: Once a doctor/swindler who robbed every medical establishment he worked for, he was not hired by Donald Blake and for revenge, he turned himself into Mr. Hyde. This could make for an interesting storyline. An interaction between Thor's alter ego in the film and Hyde, leading up to Hyde's transformation, with or without Loki being involved.
Now the Asgardian threats...
#1) Enchantress: Probably the favorite at this point, a love interest and villain for Thor. Of course there is the challenge of making a female villain who can be taken seriously. She and Skurge could be a dangerous duo.
#2) Ego, the Living Planet: While not from Asgard, an adapted version of Ego could make for some stunning visuals. Do we need the trademark beard? Maybe not, but Thor battling a planet, with or without his friends, complete with a journey across Ego, could be epic.
#3) Those Who Sit Above in Shadow: Mentioned on the tablet in Odin's vault in Thor, they are not villains per se, but Loki gets involved, and when he gets involved you don't know what could happen. They are more powerful than the Asgardians, and gain their power through the constant cycle of Ragnarok, which Thor isn't too happy about.
#4) Surtur: With the Eternal Flame in Odin's Vault, the lead-in is there, and Surtur could be fun to see on the big screen as another of the Asgardian worlds are opened, then again, he may look too much like a Balrog, and the plot may be too similar to the Frost Giants.
#5) Ymir: A continuation of the Frost Giant story could lead to Ymir, the Jotun 'all father' essentially.
#6) Malekith the Accursed: One of the Dark Elves who gets ahold of the Casket of Ancient Winters. He works with Loki and Surtur and is a master of magic.
Of course Loki's return complicates things and he can always be the puppeteer in any of these plots. Who would you like to see on the big screen opposite Thor?