In Romans 3:10, “THERE IS NONE RIGHTEOUS, NOT EVEN ONE” is like the verdict on the nature of Man. Chapters 1, 2, and 3, leading up to this verse, present arguments, as in a court case on the indictment of man on the charges of sin. Chapter 1 lays out the case against sinful man, Chapter 2 against the self-righteous; and also even against the Jews, the ones originally “entrusted with the oracles of God”. Both Jew and Gentile, circumcised and uncircumcised - in fact “ALL” have turned aside (3:12).
However, despite the solid case against man throughout these chapters, we still catch glimpses of God’s mercy and grace, in His plan for salvation: the gospel as “the power of God for salvation”, the “righteous shall live by faith, and “glory and honor and peace to every man who does good”. Romans 2:29 displays this as well, as it refers to the circumcision “of the heart, by the Spirit”.