Regarding the possibility if human sinlessness, here are three exemplary personages from the New Testament annals who might qualify:
In the days of Herod, King of Judea, there was a certain priest named Zacharias, of the division of Abijah; and he had a wife from the daughters of Aaron, and her name was Elizabeth. And they were both righteous in the sight of God, walking blamelessly in all the commandments and requirements of the Lord. (Luke 1:5-6)
although I myself might have confidence in the flesh. If anyone else has a mind to put confidence in the flesh, I far more: circumcised the eighth day, of the nation of Israel, of the tribe of Benjamin, a Hebrew of Hebrews; as to the Law, a Pharisee; as to zeal a persecutor of the church; as to the righteousness which is in the Law, found blameless. (Philippians 3:4-6)
It would be worthwhile investigating the relationship between sin and blame, especially in the context of the Jewish Law. It seems to be something like this: if you sin, then you are held responsible by God, at fault for the bad deed, under judgment and deserving of punishment. In short, if you sin, then you are blameworthy. If, conversely, you do not sin, you are not at fault, under censure: you are deemed blameless by God. I’m not sure the reader is supposed to infer that Zacharias, Elizabeth, and Paul were sinless and blameless for their whole lives. After all, the Law also specifies the means of restoring the one who has sinned to blamelessness via sacrifice, restitution, and so on.