For when we were yet without strength, in due time Christ died for the ungodly.
Note 13 at Ro 5:6: Notice the terms that Paul used to describe us before the transformation of the new birth. We were weak (this verse), ungodly (this verse), sinners (Ro 5:8), and enemies (Ro 5:10). The Lord didn't save us because we deserved it; it was an act of grace.
As great as this truth is, Paul didn't stop here. He continued on to make a comparison that if God loved us enough to die for us when we were weak, ungodly, sinners, and enemies, then much more now that we are justified (Ro 5:9) and reconciled (Ro 5:10), He is willing to save us in spite of our actions.