Paul writes of his painful visit to Corinth and the letter he sent afterwards. Even though the people in Corinth had insulted him, it was still very hard for him to write them a corrective letter. He is glad he wrote the letter, because it caused them to change their treatment of him. There must have been a specific man who had harmed both Paul and the church. The man had now apologized for the harm he caused, and Paul is encouraging the people to forgive him.
Paul was misjudged by the people in Corinth. He had tried to do the right thing but was accused of doing the wrong thing. For most, this would be very hard to forgive. The natural reaction would be to enjoy scolding them and want them to suffer. Paul does the opposite; he hates scolding them and is glad they changed their minds. Do you have someone you need to correct in a loving way? Do you have someone you need to forgive?