The Catechism in Questions & Answers

215. Why are human beings in need of redemption?

Since the fall into sin, all human beings have been sinners: they have been tempted to sin by the evil one. No human being can live without sin. Each one is mired in sin. It is from this condition that God desires to liberate—in other words, redeem—mankind.

The fall into sin and its consequences: see Questions 88. et seq.