What difference is there between the Lord’s Supper and the Pope’s Mass?

Heidelberg Catechism

Question 80. What difference is there between the Lord’s Supper and the Pope’s Mass?

Answer. The Lord’s Supper testifies to us that we have full forgiveness of all our sins by the one sacrifice of Jesus Christ, which He Himself once accomplished on the cross;[1] and that by the Holy Spirit we are ingrafted into Christ,[2] who, with His true body, is now in heaven at the right hand of the Father,[3] and is there to be worshipped.[4] But the Mass teaches that the living and the dead do not have forgiveness of sins through the sufferings of Christ, unless Christ is still daily offered for them by the priests, and that Christ is bodily under the form of bread and wine, and is therefore to be worshipped in them. And thus the Mass at bottom is nothing else than a denial of the one sacrifice and suffering of Jesus Christ,[5] and an accursed idolatry.

[1] Mt 26:28; Jn 19:30; Heb 7:27, 9:12, 25-28, 10:10-12, 14; [2] 1 Cor 6:17, 10:16-17; [3] Jn 20:17; Acts 7:55-56; Heb 1:3, 8:1; [4] Lk 24:52; Jn 4:21-24, 20:17; Acts 7:55; Php 3:20-21; Col 3:1; 1 Thes 1:9-10; [5] Mt 4:10; Heb 9, 10