'Adversary' in the Bible

Or, Deliver me from the adversary's hand? Or, Redeem me from the hand of the oppressors?

He hath torn me in his wrath, and persecuted me; He hath gnashed upon me with his teeth: Mine adversary sharpeneth his eyes upon me.

Oh that I had one to hear me! (Lo, here is my signature, let the Almighty answer me); And that I had the indictment which mine adversary hath written!