The Gospel is a declaration by God that his Son Jesus Christ has victoriously defeated sin, death and the devil and now sits in heaven as... "The King of Kings and the Lord of Lords" Revelation 19:16.
All that Jesus is, and all that Jesus did, he did in our name and on our behalf. In Jesus Christ we have been justified, sanctified and redeemed and now stand in God's Holy Court as perfect and complete "In Christ" Colossians 2:10. In Jesus Christ the law has been fulfilled, Matthew 5:18 and abolished, Ephesians 2:15.
Catholicism is a denial of this Gospel and justification by faith alone. We are justified by faith alone, because we are justified by Christ alone, Jesus justifies the ungodly, Romans 4:5 and reconciles them unto God, 2 Corinthians 5:18-19. Making us complete in himself, Colossians 2:14. Jesus Christ is not only the end of the law for righteousness, Romans 10:4, He is the end of all religions.