I figure you mix two very different concepts of "duality", first is anatomy concept of duality between two brain hemispheres, this duality indeed ends in singularity, i.e. singular organ of human body which is called brain and you don't need to be enlightened to understand this it is a common sense, something obvious.

Second concept of duality is metaphysical one , it is best known as an opposition between the good and the evil. Then, there are two main theories concerning this duality, first is best known as zoroastrian/manichaean dialectic which claims that the duality is natural and eternal and the opposition between two dual terms cannot be reconciled; second is best known hegelian/aristotilean dialectic which claims that the duality is only a part of a universal development and its oppositions will eventually be reconciled in the universal union. Whether manichaean or hegeian theory is right is not obvious at all.

So, there is that old rhetorical trick, take two homonyms and extend attributes of one homonym to another. You seem to use exactly this trick, deliberately or not: you take word "duality" as it is being used in anatomy and extend its attributes and definitions on the word "duality" as it is being used in metaphysics. I don't want to say that you are lying or that your theory about inexistence of duality is wrong but your line of reasoning is indeed doubtful.

And you didn't answer my first question, if duality doesn't exist then where evil, that is, the illusion of duality and the group of people who controls and exploits this illusion came from.