Exactly what was accomplished by the cross? according to Catholic doctrine?
Christ Jesus died for ALL sins PAST, PRESENT and FUTURE: and all sins which were laid upon Him in the 1st Century from our perspective are FUTURE sins. Therefore, no sin that men / women commit today for a believer, is not unforgiven; everything is paid in full.
Colossians 2:13: And you, being dead in your sins and the uncircumcision of your flesh, hath he quickened together with him, having forgiven you all trespasses;
Christ has forgiven you all trespasses (and sins): paid in full at the cross. That is what was accomplished at the cross.