Christ's death is the unique and definitive sacrifice
Christ's death is both the Paschal sacrifice that accomplishes the definitive redemption of men, through "the Lamb of God, who takes away the sin of the world", and the sacrifice of the New Covenant, which restores man to communion with God by reconciling him to God through the "blood of the covenant, which was poured out for many for the forgiveness of sins".
Source: Catechism of the Catholic Church (Vatican.va)