It is not a case that sin brightens the picture but because evil took on sin that resulted in evil being sentenced to death. The whole time the seed of the serpent is consuming the dust of the earth that makes up our physical bodies, the thorn in our flesh that is Satan's messenger in us aka the law of sin is already self-destructing. This is the beauty within God's plan; because evil already had to exist in the spiritual realm, but then when it appeared in the physical realm, by becoming sin it was sentenced to death.
The commandment given to Adam was if they ate of the tree of knowledge of good and evil was that day they would surely die. They died physically that day because they did not live out the 1000 years that is the day. They also died spiritually that day by being separated from God because of their sin that took on death and separation from God.
While on one hand death is a result of sin; the death that is a result of sin brings forth more sin because once one leaves the presence of God that is the only thing that can withhold sin, sin rules over them. Therefore, the sting of death is sin because once we are separated from God we are in a state of death and there is nothing left to withhold sin.
However even when sin continues unchecked in its cancerous assault on humans it is self-destructing because the only place it can exist is in the unclean spirit and soul of Adam and Eve who became one flesh.
Because as the Scriptures say before the foundations of the earth were laid the morning stars jumped for joy, there was a plan made for evil to be destroyed (learning to hate evil is part of the beginning of wisdom). In the begining Adam could not sin because both he, and God who cannot sin, were both of the same Spirit. The statement in the verse saying they communed in the cool of the day translated means they communed in the spirit because the same spirit that gave Adam life from the breath of God was the spirit of God.
As long as the Spirit of God was in charge in Adam, he could not sin. Therefore there had to be a change made that would allow Adam to sin that is something he was not capable of doing when first created.
This is where the phrase "made subject to vanity" comes into play that when translated means Adam was altered so that he could not perform as he had been originally created to perform.
Romans 8:20
For the creature was made subject to vanity, not willingly, but by reason of him who hath subjected the same in hope,
The above verse speaks of when God changed Adam that made Adam's sin a foregone conclusion, and not a matter of if but a matter of when.
This happened when God caused a deep sleep to come upon Adam and a bone was taken from him that was used to form Eve. To try to shorten this long story a little bit I'm going to hope that this point you can see that at this point the flesh of Adam was given a mind and a voice of its own that is something that was not coming from Adam before he sinned, because before Eve, Adam only followed the mind of Christ he was first created with that could not sin.
However when Adam followed the voice of Eve who that was taken from his flesh that used the senses within the flesh to determine what was good or bad, instead of continuing on with following the commandment of God, Adam deliberately made a decision contrary to the commandment of God, therefore sin and death entered into all of mankind
However, his decision resulted in evil becoming sin that got it sentenced to death. Consequently, and for the first time since both good and evil were both created by God,(
Isaiah 45:7) evil started to destroy itself.
The plan was/is absolutely brilliant and only God in heaven could ever come up with such a plan (why the morning stars, aka sons of God jumped for joy;
Job 38:7 ) let alone put it into effect (or as the verse above says, "subject the same unto hope)
God has accepted responsibility for man's sin and is why He appeared on earth in human form to suffer and die for us. We can deal with what hell is all about at a later time, meanwhile if you would do a search on the times the word "hell" appears in Psalms and how it is used will help.
Blessings
Doug