Before the fall - Adam was created with a free will and power to choose right and wrong.
The Devil was created perfect and iniquity was found in his heart. He likewise had free will. He rebelled against God and was cursed as a result of his rebellion.
Ezekiel 28:15...Thou wast perfect in thy ways from the day that thou wast created, till iniquity was found in thee.
When Adam fell - God's curse from the fall took place and two things happened. The Messiahship of Christ was promised to the serpent who deceived Eve; every man born into humanity would be born with indwelling sin no longer with a free will but bound by a sinful nature from birth.
Romans 5:19...For as by one man's disobedience many were made sinners,
The divine nature was lost. Man became carnal by nature with a corrupt will. Paul wrote man's inherited state was described as, "Carnal sold under sin".
Romans 7:14...but I am carnal, sold under sin
Romans 7:20...Now if I do that I would not, it is no more I that do it, but sin that dwelleth in me.
