That's an interesting question. The first thing that comes to mind is the Gnostic Demiurge (named as Yaldabaoth, Saklas, or Samael depending on who you're asking; there are other names), the explicitly unFriendly creator spirit who is nonetheless not an embodiment of evil as per Satan or Angra Mainyu.

I'm not sure if there are any good type specimens for "unFriendly god", though. It's not hard to find spirits of evil in polytheistic or henotheistic religions, but using one of those names would carry unwelcome implications, and while a decent working definition for "god" in a number of polytheistic pantheons might be "a bigger jerk than most everyone else", using someone like Thor as an example would imply polytheism before it implies unFriendliness.