Why is Christ's sacrifice on the cross considered the greatest day of all?

The significance of Christ's sacrifice on the cross transcends the repetitive ceremonies of the Old Testament. Unlike the Day of Atonement that required annual repetition, Christ's one-time sacrifice addressed the root problem of sin, achieving eternal redemption and perfecting those who are sanctified (Hebrews 10:14). This event marked the culmination of God's redemptive plan, as it represents the day on which Jesus declared, "It is finished!" (John 19:30), thus abolishing the old covenant and inaugurating a new, everlasting covenant by the shedding of His blood. This makes the day of the cross the focal point of all of redemptive history.