Mummelmann on 17 February 2014
If you go by the first time you encounter them; I'd say probably a Giant. The Dragons aren't really any hazard in Skyrim since they're really stupid and incredibly slow on the ground.
Sabretooth are also really dangerous in the beginning.
After you've reached level 30+ though; nothing is dagersous any longer and that's one of my main gripes with this game and most games in this genre and that's on of the reasons why I prefer the isometric, tactical RPG's of yore.
