In the sin of Adam, the federal head or representative of all humanity, all humanity was declared sinners. Sin was imputed to the human race in Adam. This was evidenced by acts of sin, and sin nature, and the universal reign of death.

What is the effect of one man?

From Adam, the legacy was sin and death imputed to the human race. On the other hand, the free gift of the gospel of grace can overcome death to eternal life through another one man, the second Adam, Jesus Christ.

https://youtu.be/ty4s5blQGZ4