We find in 2 Corinthians 10 that in Paul’s absence there were those who spoke against his authority, and against him as a person. These attacks seem to have come only in his absence, not in his presence. Verses 8-10 shed light on the nature of the attacks:
“For even if I boast somewhat further about our authority, which the Lord gave for building you up and not for destroying you, I will not be put to shame, for I do not wish to seem as if I would terrify you by my letters. For they say, “His letters are weighty and strong, but his personal presence is unimpressive and his speech contemptible.” Let such a person consider this, that what we are in word by letters when absent, such persons we are also in deed when present.“