Why there is no concept of Satan (a permanent entity who always act against God) in H

Do you think there can?t be permanent enemy of God? Or do you think there should be some permanent enemy for God?

(In past, some Asura?s who went against God finally surrendered to Bhagavan, agree?)
@ use your brain,

Actually Bali is a Darya (Asura) not a Satan. Finally Bali surrendered to God (Mahavishnu)

For more info you can read this story.
http://moralstories.wordpress.com/2006/05/31/bali-chakravartis-story/

Because in Hinduism, as in most Pagan religions, there is no concept of dualism. God cannot be divided against itself, hence there cannot be a Satan.

you are wrong.
devil is known in Hindu Bali

SAT and ASAT exist always and both are creation of GOD

The entire Hinduism itself is Satanic and against the Reality - The Truth. Satan will not write against himself. Hence there is no mention or concept of Satan in Hinduism.

Well from my point of view, everything is relative, even we look the world as there must be always a dual.

For the most people there is day and night, for me there are many other stages. For the most people there is man and women, for many other religions there are more genders. For the most people there is Good and Evil, for me Good and Evil can act indistinctly because everything is relative.

When the Universe was created there was a little bit more of matter in relation with antimatter, otherwise everything would be annihilated. so even in physics there is not dualism, there is an "anti" for everything but it doesn't mean the world works on dualism.