I'm not really a Thor fan, but I have to admit that Thor has one of the best "rogues gallery" of any superhero, his villains are an interesting bunch, not the most complex (except Loki) , but certainly very colourful and the source of
many great stories.
The Wrecking crew are definitely a great idea, and the Absorbing Man, and the Enchantress, and the Executioner. I would love to see those guys on the big screen.
BUT.....if we're talking Ragnarok (n roll) we have to get all Simonson on this bad-boy, which means we need......
It's a logical follow up to the Dark Elves, and that classic story was also famous for a Thor + Loki + Odin team up, which would be a great way to
resolve their issues.
To be honest, I don't know the God-butcher (art looks cool though) or Desak or Perrikus, so really, they don't really count for me. Besides, the Simonson stories are classics for a reason, (weren't the Dark Elves superb in TDW ? I thought so)
The Celestials ? They're basically God and his cousins, and not necessarily villains, so probably not what I'd consider villains for Thor to take on.
But Surtur, he's straight out of Norse Mythology's version of hell (and looks like it too). Can't you see Hemsthor, Hiddleston and Hopkins taking on a 1000 foot tall demon....sheer awesomeness !