Yamaraja is explaining that "He is above me, the supreme controller, and He is the..., He is such controller that He creates, He maintains, and He annihilates also." We become so much harassed even for creating a family and maintaining them. We have become so much harassed. And foolishly we claim that we are the Supreme Personality of Godhead who creates the whole cosmic manifestation. And Brahma, Visnu, Mahesvara, the directors of creation department, maintenance department, and annihilation department... Annihilation also required. That annihilation is one of the business of Krsna, or God, for this material world. Not in the spiritual world. There is no annihilation. Here it is required. Sometimes, because everyone has come here to lord it over the material nature, so there must be an ultimate situation when it becomes intolerable, and therefore Krsna has to annihilate, finish. That is kalki-avatara.
Lecture on Srimad-Bhagavatam 6.3.12-15, Gorakhpur, February 9, 1971