AncientWord

Is the book of Galatians the most scathing attack ever launched by Paul? Right from the introduction, Apostle Paul is not just introducing any other letter. He asserts immense authority, vigor, passion and unmatched rebuke to the people of Galatians. Perhaps that's why we never had the second book of Galatians.

Summary of the Book of Galatians

Galatians Chapter 1 — Shock and Defense of Apostleship

Unlike the book of Philipians or Corinthians, Paul opens up unusually abrupt and ready for war. He asserts his preaching authority and boldly states it's not from men but from God the Father and the God the Son.
He proceeds to express his shock at how the Galations were quick to running away from the one who called them (v1.6). Paul reiterates that his gospel is from God and if anyone were to preach a different gospel he must be cursed. Pauls sounds wounded, angry and urgent.

Galatians Chapter 2 — Conflict and Apostolic Independence

Paul begins chapter 2 of his visit to Jerusalem just to ensure he was in spirit with the gospel the other apostles were preaching. For 15 days meeting Peter and James (Jesus' brother), he says he already got it right, they added nothing. He lets us know that he openly rebuked Peter when he lived a pretensful life. And concludes the chapter by reiterating that salvation is by faith to Lord Jesus and not by works of the Law. 
Paul sounds combative, bold and ready to defend the gospel he preaches at all cost.

Galatians Chapter 3 — Faith vs. Law

Perhaps the strongest confrontation we ever saw of Paul. He introduces the chapter with "O foolish Galatians! Who has bewitched you?” 
A people who received the Spirit by faith and now turning to the law, how can that work? He goes on to use Abraham: Abraham was justified by faith before circumcision. Abraham came first and then the law later just to expose sin and justify salvation in Christ. Paul concludes the chapter by asserting now, all are sons of God through faith; no Jew/Greek, slave/free, male/female—one in Christ
Paul sounds fiery in logic, reliant on scripture and escalatory in passion.

Galatians Chapter 4 — Heirs of Promise, Paul’s Anguish

Paul brings the sense of adoption through Christ. However, pleads fears: “I fear I may have labored over you in vain.” Paul takes them down the memory lane perhaps to invoke repentance emotions. He reminds tthem how they once welcomed him despite his bodily illness, even to a point of offering their eyes. And yet now they are treating him like an enemy and concludes by using the allegory of Hagar and Sarah to express freedom by promise.
Paul sounds he is in deep sorrow, filled with paternal anguish and appealing.

Galatians Chapter 5 — Freedom and the Spirit

Paul  declares it's freedom in Christ that sets men free and therefore if they accept circumcision, the freedom in Christ is useless. He feels his sheep has been sharply unsettled and lays a curse wish on them "I wish those who unsettle you would castrate themselves!” (5:12). Paul for the first time in the book links the law and any work of the flesh to evil doing amongst many and constrasts it to works of the spirit by faith.
Paul is explosive, sarcastic, and urgent in his call for firm standing.

Galatians Chapter 6 — Bearing Burdens and Closing Marks

Paul considers those those who accepted circumcision as fallen and offers practical instructions: restore the fallen gently, bear one another’s burdens, sow to the Spirit not flesh. He goes on to warn the fallen not to boast of the circumcision rather boast in faith in Christ. Paul is very emotional and appealing, See with what large letters I am writing with my own hand! From now on let no one cause me trouble, for I bear on my body the marks of Jesus.
Paul sounds pastoral, weary, scarred but still blessing.

Why Did Paul Write the Book of Galatians; Why Paul was so Mad in Galatians:The Judaizers' Influence

Apostolic Authority in Paul

The Marks of Jesus on Paul

The Thorn in Paul's Flesh

The Spiritual Stakes: Freedom vs. Slavery [Law vs Faith]

Conclusion and Why no Second Galatians