I don't have any god that's the 'devil' to me, and I think it's a pretty absurd position to take - all thinking gods supposedly have their positives and negatives.
But, if it's a god I see as an antagonist - probably Jas. She spawns civilizations for dinner and has genocide for breakfast. She doesn't clean up her toys, then obliterates anyone who plays with 'em. All creation is just a means to feed herself and her progeny.