Chapters 1 & 2.
Though we call this 1 Corinthians it is in fact the second letter he wrote to them;
1 Cor 5:9; I wrote unto you in an epistle not to company with fornicators.
Paul begins by establishing his authority within the Kingdom of God. He claims his calling and authority to be from the highest source, namely God. He had not sought or fought for this ministry or position . It was the will of God, not his. (see Galatians ch 1 v 1.)
It is worth checking out other epistles to see a similar opening;
Sosthenes : Could be the same as in Acts ch18 v 12-17, but no real evidence available;
Paul gives a glowing summary of the State of the Corinthian church at the beginning, yet as we examine the contents of the letter, Paul found plenty of issues to set before them.
May be it was the case that a few, acting in the flesh were the cause of most of the shortcomings. As in Galatia, maybe a little leaven was in danger of leavening the whole lump. Perhaps however, we may be seeing a very human trait which is to “soft soap” the Corinthians to get their attention, before he scrubs them down.