Jamieson, Fausset and Brown on 2 Peter 1:7

7. "And in your godliness brotherly kindness"; not suffering your godliness to be moroseness, nor a sullen solitary habit of life, but kind, generous, and courteous [Alford]. Your natural affection and brotherly kindness are to be sanctified by godliness. "And in your brotherly kindness love," namely, to all men, even to enemies, in thought, word, and deed. From brotherly kindness we are to go forward to love. Compare 1Th 3:12, "Love one toward another (brotherly kindness), and toward all men (charity)." So charity completes the choir of graces in Col 3:14. In a retrograde order, he who has love will exercise brotherly kindness; he who has brotherly kindness will feel godliness needful; the godly will mix nothing stoical with his patience; to the patient, temperance is easy; the temperate weighs things well, and so has knowledge; knowledge guards against sudden impulse carrying away its virtue [Bengel].