Do you agree that "The greatest trick the Devil ever pulled...?

Yes, the devil would make you believe that he does not exist and in the long run, he'll make you believe that God then does not exist. If the devil does not exist, then there can be no concept of sin, evil or wrong. If there's no concept of sin, evil or wrong, then there's no concept of good. And if there's no concept of good, there's no concept of God. And without faith, you cannot be saved. Your soul is his for the taking.