The cross, and what Jesus did on the cross, is enough to satisfy and uphold the demands of God’s righteousness against the sin and sinners of today, yesterday, and forevermore.  Nothing else is needed.  It has already been proven that nothing else will do:

“Neither by the blood of goats and calves, but by his own blood he entered in once into the holy place, having obtained eternal redemption for us.

For if the blood of bulls and of goats, and the ashes of an heifer sprinkling the unclean, sanctifieth to the purifying of the flesh:

How much more shall the blood of Christ, who through the eternal Spirit offered himself without spot to God, purge your conscience from dead works to serve the living God?” Hebrews 9:12-14

At the time of His death, all sin, past, present, and future, were placed upon our Savior as He hung on that cross.  It’s what one does with the revelation of the cross for their own life that makes all the difference.