SB 10.2.29
bibharsi rupany avabodha atma
ksemaya lokasya caracarasya
sattvopapannani sukhavahani
satam abhadrani muhuh khalanam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
O Lord, You are always in full knowledge, and to bring all good fortune to all living entities, You appear in different incarnations, all of them transcendental to the material creation. When You appear in these incarnations, You are pleasing to the pious and religious devotees, but for nondevotees You are the annihilator.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
This verse explains why the Supreme Personality of Godhead appears as an incarnation again and again. The incarnations of the Supreme Personality of Godhead all function differently, but their main purpose is paritranaya sadhunam vinasaya ca duskrtam to protect the devotees and annihilate the miscreants. Yet even though the duskrtis, or miscreants, are annihilated, this is ultimately good for them.