2 Corinthians is the most emotionally raw of Paul's letters, written after a relationship with the Corinthian church that had badly deteriorated since 1 Corinthians. Paul refers to a "painful visit" and a "letter written in tears," neither of which survives, and spends much of the letter defending his own conduct and authority against rival teachers who had apparently won a hearing in Corinth by presenting more impressive credentials, better rhetoric, letters of recommendation, visionary experiences, than Paul himself offered. His response inverts the usual terms of the argument: rather than matching the rivals' boasting, he "boasts" instead of his beatings, shipwrecks, hunger, and a mysterious "thorn in the flesh" that God refused to remove, concluding that "power is made perfect in weakness."
Chapters 8 and 9 shift tone entirely to appeal for the collection Paul was gathering from Gentile churches for the poor in the Jerusalem church, framed not as an obligation but as an act of grace modeled on Christ's own self-emptying. The final four chapters, 10 through 13, turn sharply harsher and more sarcastic than anything before them, a shift in tone abrupt enough that many scholars read it as a separate, angrier letter later joined to the rest.