The background to 2 Corinthians is complicated by letters from Paul we do not have as well as visits to Corinth by Paul, Timothy and Titus. An additional problem is 2 Corinthians is a compilation of several other letters. Perhaps parts of 2 Corinthians contain other letters sent by Paul (the so-called “tearful letter”). Some suggest chapters 8 and 9 are separate letters dealing with the collection, and chapters 10-12 are yet another letter dealing with the super-apostles. I would recommend any serious commentary on 2 Corinthians for an overview of these suggestions or an introduction to the New Testament such as Raymond Brown. Combining letters around a similar theme is not surprising, but it is also not necessary to understand the overall theme of the whole letter: the need for reconciliation between Paul and the church.
First, Paul must deal with the damage in his relationship the Corinthian church (2 Corinthians 1-7). The church did not receive the letter of 1 Corinthians well and Paul’s attempts to deal with the tensions seem to have created more problems. The reason Paul did not return to Corinth is to spare them from another difficult visit (1:23-2:1). Paul admits he has caused the church a great deal of pain, but (with God as his witness), he did not intend it that way. Although he does admit he may have caused the pain the church felt after 1 Corinthians, the “tearful letter” and the painful visit.
Paul wanted to gladden those he had pained, but the pain was ultimately necessary. His tough letter was written to make it possible for him to have a “joyful visit” the next time he came to Corinth (2:3). Paul was confident the church world respond to his tearful letter, even if there was come fear it might cause them pain. But not all grief and pain is bad, in fact godly grief produces a great deal of positive virtues. If Paul had upset them with his strong challenge, that pain is a positive benefit if they are reconciled to him
Second, Paul must encourage the Corinthian church to make good on their promise to participate in the collection he has made for the poor saints in Jerusalem (2 Corinthians 8-9). Paul’s collection would have looked very suspicious to a resident of a Roman city like Corinth. Public works were not funded through taxation or public fundraising, but through wealthy people who want to gain honor from public benefaction. There is no honor in putting money into general fund and sending it off to distant (non-Roman) city to be used to help poor people. It is no surprise at all the Corinth church was slow to participate in the Collection. But it is remarkable (from a modern Christian perspective) this wealthy Christian church refused to participate in Paul’s collection to help the poor Christians in Jerusalem. But now that Paul and the church have reconciled, it is now time for the church to participate in this important ministry Paul initiated. In fact, for Paul, participating in this gracious gift is an opportunity to render a service to God.
Third, Paul must deal with some competition in the church, the so-called “super-apostles” (2 Corinthians 10-13). Paul probably coined this sarcastic description of his opponents, but it may be based on the attitude of the opponents themselves. They consider themselves to be superior to Paul in terms of honor, use of rhetoric, and perhaps even blessings from God. Some have argued this is a reference to the apostles in Jerusalem, but it seems unlikely Paul would refer the Twelve with this snarky title. More likely the super apostles are Greeks in Corinth who have accepted the Gospel but are now behaving like Greek intellectuals. Like many of the other issues in Corinth, Paul is dealing with a pagan worldview in the church. The opponents appear to be trained communicators (v. 6) and accepted patronage from the church (v. 7-9). This would be consistent with any other Greco-Roman philosopher or teach and more or less expected by the Corinthian congregation. Rather than superior apostles, the opponents are like Satan, masquerading true apostles (11:12-15). Rather than boast in his accomplishments, Paul choose to boast in his suffering as a servant of Jesus Christ. Boasting in beatings and arrests is an outrageous reversal of what the super-apostles consider to be indicators of divine favor. Paul claims in these final chapters of the book that the follower of Christ can expect to suffer as Christ himself did.