What is Paul especially doing in the Corinthian letters compared to his other letters?
In the Corinthian letters, Paul is especially defending his apostleship, more than in his other letters. Everywhere he went, Judaizers challenged him by claiming Peter had spent three years with the Lord and was their spokesman, so Paul repeatedly had to defend his apostolic authority.
Les explains that all the way through the Corinthian letters, Paul is especially, more than in the others, defending his apostleship. This was necessary because every place Paul went, the Judaizers would say that Peter had spent three years with the Lord, that Peter was their spokesman, and that Peter was the one they would listen to. Les also notes that Paul came under satanic opposition from every possible direction as soon as he began his ministry among the Gentiles. In chapter 4, Paul grew weary and almost despaired of life itself, feeling as though he was just getting the gospel off the ground and everything fell in on him.