Understanding how agency works will help us understand how Satan sought—and seeks—to undermine it. Agency requires three things: options to choose from, freedom to choose, and consequence for the choice. Like a three-legged stool, agency can be weakened or destroyed (in theory) by attacking any one of the three.
Let’s also establish an important point: no scripture mentions Satan forcing people to be righteous. Further, we read that Lucifer told Heavenly Father, “I will be thy son, and I will redeem all mankind, that one soul shall not be lost.” Consider this question: if Lucifer intended to coerce obedience to God, then why did he propose to redeem us? Redemption would not be necessary under a system of compulsory obedience. This admission on Satan’s part makes clear that his proposal included options to choose from, and the freedom to choose—the two conditions that would make redemption necessary at all.
It therefore follows that Satan’s proposal sought to undermine the third: consequence for the choice.