1 Now I, Paul, myself am pleading with you by the meekness and gentleness of Christ—who in presence am lowly among you, but being absent am bold toward you.
—who in presence [personal appearance] am lowly [timid] among you,
Paul’s enemies claimed that he was weak in bodily presence (2 Co 10:10). These men insinuated themselves into the Corinthian church, undermining his authority as an apostle (2 Co 11:1-15). They claimed that, while Paul was physically present in Corinth, he showed himself as weak, and that only when he was a safe distance was he courageous.
but being absent am bold toward you.
Paul’s enemies claimed that, while he was away from Corinth, he was bold toward them in his writings. The implication from his enemies was that Paul was courageous when he wrote but was timid while in Corinth in person. The purpose of his enemies was to subvert his authority, especially his apostleship. The idea is that Paul’s enemies said that he talked big in his writing but was weak kneed in person.
Paul’s opponents sought to undermine his reputation, and they magnified themselves. They distorted facets of Paul’s character and work and blew them out of proportion. They attacked his appearance and his methodology. Paul was probably a small man physically. Someone said about him, “Three cubits high, he touched the sky.”
Some people will attempt to undermine those in leadership.
Leadership requires sagacity. It is crucial to understand and know how certain people approach life. Some want to undermine any authority that threatens their biases. It is not a matter of not trusting people; we should always give others the benefit of the doubt. Love believes the best about people (1 Co 13:7, see https://versebyversecommentary.com/2002/12/27/1-corinthians-137b/ ). But neither does this mean that we lead with naivety.