Jamieson, Fausset and Brown on 2 Corinthians 2:4

4. So far from my change of purpose being due to "lightness" (2Co 1:17), I wrote my letter to you (2Co 2:3) "out of much affliction (Greek, 'trouble') and anguish of heart, and with many tears."

not that ye should be grieved--Translate, "be made sorry," to accord with the translation, 2Co 2:2. My ultimate and main object was, "not that ye might be made sorry," but that through sorrow you might be led to repentance, and so to joy, redounding both to you and me (2Co 2:2, 3). I made you sorry before going to you, that when I went it might not be necessary. He is easily made sorry, who is admonished by a friend himself weeping [Bengel].

that ye might know the love--of which it is a proof to rebuke sins openly and in season [Estius], (Psa 141:5; Pr 27:6). "Love" is the source from which sincere reproof springs; that the Corinthians might ultimately recognize this as his motive, was the apostle's aim.

which I have more abundantly unto you--who have been particularly committed to me by God (Ac 18:10; 1Co 4:15; 9:2).