The most obvious problem with the quoted excerpt is that the Scripture never mentions one getting his or her sins forgiven through a complex church hierarchy. It is given by a Person, and His name is Jesus Christ (John 14:6; Acts 4:10-12). Our sins are washed away by His shed blood (Hebrews 9:13-14; 1 John 1:7-9; 1 Peter 1:19; Revelation 1:5). We are justified by accepting the gospel, which nowhere demands a complex hierarchy. It is He who has mercifully paid our sin debt in full (Matthew 18:23-35). The mercy of God is not limited to an institution or a set of rituals. Nowhere does Scripture say that His grace is imparted or communicated through some hierarchy. It is simply wrong for the Church of Rome to maintain that He has bestowed upon it some sort of power and authority to pardon our iniquity.
Other existing problems about the quoted excerpt from the Catholic catechism above are probably not as readily apparent to a cursory reader. The Lord Jesus Christ does make mention of the unpardonable sin, which is blasphemy against the Holy Spirit (Mark 3:28-29). So it is not true that the Roman Catholic Church has the power to absolve sin, "no matter how serious the action in the sight of God." Moreover, we know that Rome does not have any ability to forgive our sins because only God knows the hearts of man (1 Samuel 16:7; 1 Kings 8:37-39; 2 Chronicles 6:30). To claim that the Roman Catholic Church has the authority to forgive sins is to place a human institution in the place of God, and so is presumption in the highest degree.