2 Corinthians 12:21 expresses Paul's fear of mourning over unrepentant sinners; the grief in 2 Corinthians 2:5 is from a disciplined offender, a contrasting outcome.

2 Corinthians 7:3 affirms Paul's deep love for the Corinthians, which underlies his pastoral handling of the grief caused by the offender.

1 Corinthians 5:1-5 describes the incestuous man and the church discipline that caused the grief Paul now mentions. It provides the background context.