en_tn/ezr/09/13.md

our evil practices and our great guilt

Israel did not utterly destroy the people practicing evil before God. Israel began marrying them and following their religious practices being led astray from God.

since you...have held back what our iniquities deserve and left us survivors

This is an example of God's mercy in action.

should we again break your commandments

This was exactly what some of the returnees have done. They broke God's commands by marrying the people of the land and worshiping their gods.

Will you not be angry and annihilate us

God destroyed all of Israel before and Ezra feared that He would do it again and then there would no one left.