Does Satan Warrant Defeating?

Is the Devil ultimately defeated? Under the Christian plan, the Devil is vanquished forever after the second coming of Jesus Christ. I like the idea of eternal change, motion and many, unlike the Parmenidean conception of ultimate reality as One, eternal, unchanging, motionless. Because becoming is all agents growing and developing, the ultimate defeat of the Devil may not be desirable, and the total, ultimate, unending defeat of evil by good and God may not be desirable, perhaps even possible. My moderate ontology makes me believe that God is a bit evil and the Devil is a bit good, so that they understand each other. Change is vital for moral growth, for free will to have meaning, neither God or the Devil can or must win eternally. Were God to enjoy final, ultimate victory over Satan, forever God’s followers would be good robots, but not knowing or exercising free will. Were Satan to enjoy final, ultimate victory over God, pure nihilism and pure chaos would blow up the ordered cosmos, and Satan’s minions, would be purely wicked robots, without a scintilla of free willing going on in their minds. Without the eternal battle between good and evil, new generations of sentient beings would not have a purpose, no moral aim to strive towards, and free will is a meaningless concept.