Romans 5:21

²¹ so that as sin reigned in death, even so grace might reign through righteousness to eternal life through Jesus Christ our Lord.

This verse presents a double contrast — sin and grace reign — death and righteousness are the results.

Death is the order of the day in sin’s reign, but righteousness is the order of the day in grace’s reign to those who believe (verse 17).

God’s righteousness reckons the believer righteous on the grounds of Jesus Christ’s death.