What did Christ's resurrection power accomplish against Satan?
Christ's resurrection power bruised Satan's head, putting him into a place of defeat. The seed of the woman crushed the serpent's head, the only place a snake can truly be killed. Satan still bruised Christ's heel by causing His suffering for salvation, but the resurrection secured the decisive victory.
Les explains that as soon as man sinned, God came back with the remedy: the seed of the woman, the Christ, the Son of God. That remedy came by Christ being crushed or put to death at the cross, whereby His power of resurrection and all that it implied would bruise Satan's head and place him in defeat. Les clarifies that the seed of the woman would bruise the head of the serpent, which is the only place a snake can really be killed. Yet Satan would still bruise His heel, causing the suffering Christ endured for our salvation.
And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel.