The Catechism in Questions & Answers

640. What is meant by the words “Deliver us from the evil one”?

This plea expresses the desire that God may deliver the believers from the power of the evil one. Ultimately it is a plea for God to grant ultimate redemption by delivering us from the evil one forever. In the Son of God “we have redemption, [...] the forgiveness of sins” (Colossians 1: 14).

Evil: see Questions 217. et seq.