I was recently re-watching the Star Trek: The Next Generation episode Masks, (because I'm not a nerd even a little bit), and an interesting thought struck me: the culture portrayed in that episode seems to have had a pantheon centered around an incredibly cruel, if not outright evil, torturer-Queen deity named Masaka. The other gods from her pantheon seem to either be hiding from her, fearing her, or trying to counter her influence. This is not unlike the episode Devil's Due, in which another society seems to hold the negative deity, a devil-figure named Ardra, above all others.
It made me wonder, have any historical cultures revered a negative or evil deity as their primary or most-powerful figure? Obviously plenty of primary deities (such as Zeus or Odin or even the Old Testament Yahweh) have been shown to be cruel, callous, or capricious at times, but these gods are also heavily tied to ideas like justice, courage, or mercy. They are, ultimately, positive forces in the universe and toward humanity.
Have any societies held a strictly evil or malevolent deity above all others?
EDIT: In response to several commenters, I thought I'd clarify: I'm talking about gods whose own worshippers considered the god a force of evil, not those who are interpreted as such by outsiders, and certainly not a discussion of whether religion itself is positive. I'm saying that Zeus, Odin, and the Judeochristian God are all viewed by their followers as "good." Were any pantheon-topping gods seen by their own worshippers as primarily malevolent, rather than benevolent?