Good thing superhero sequels aren't notorious for being cluttered with unfocused villainy, or I'd have to make some sarcastic reminder of that.
Mads Mikkelsen, the Danish actor who has already played villainous and/or worn armor in Casino Royale and Clash of the Titans, is said to be in negotiations to take on a bad guy part in Marvel's upcoming Thor 2. It's still unclear what villain he would be playing, but he'll be fighting alongside Tom Hiddleston, who is confirmed to be returning to do mischiefs as Loki. Here's a list of Thor villains to start blindly guessing at the part. I'm calling Handsomer Mangog right now.
Also in Marvel villain casting news: Ashley Hamilton--described as "a personal friend of Robert Downey Jr." and "son of George Hamilton," even though he's clearly the product of a baffling experiment in melding Jason Patric and Peter Weller into a tooth-whitening spokesman--is reportedly in talks to join Shane Black's Iron Man 3 as "one of the villains." He would play Firepower, a cyborg in a powered suit created by a clandestine government program. Hamilton would join fellow villain Ben Kingsley and also fellow government cyborg Coldblood, which sort of hints that maybe Iron Man is going to be fighting a bunch of government cyborgs. Jon Favreau has also been confirmed to return to the franchise as Happy Hogan, though there now exists the increasing chance Happy will be made even portlier with cybernetic attachments.