To re-establish Dharma (righteousness) and root out evil forces of adharma (lawlessness), Kalki avatar could go to any extent world over. Kalki avatar is not a harbinger of destruction. On the other hand Kalki avatar is a messiah of peace and harmony world over.
If the world has degraded to a point of no return, whose fault it is, definitely not of Kalki avatars. Kalki avatar could only set things right for the people, of the people and by the people.
Even before advent of Kalki, before surfacing of Kalki avatar mankind is doomed to destruction. It is not Kalki avatar who would bring about start of world war 3. The world war 3 is in making due to obnoxious practices indulged by practitioners of both Christianity and Islamic Dharma.
It is only in aftermath of world war 3 Kalki avatar would bring about a significant change in world scenario. After death of about 1200 million people in world war 3 the entire world would practically convert into a mass grave. In such circumstances humanity awaits a soothing balm to their hurt feelings. Mounted with jnana wisdom of Bhagavad Gita and Upanishads (independent spiritual treatises) Kalki avatar would bring peace to all, the so much needed inner calm.
The might of Kalki avatar would be recognized worldwide only in the aftermath of world war 3 but in India situation would be different. Kalki avatar would be active in India from the very beginning. The lone crusader of truth would assert his authority to re-establish Dharma (righteousness) initially starting from India and finally it would spread to every corner of world.
It is Kalki avatar who would usher present mankind into Satyuga, the awaited golden period. In the circumstances how can Kalki be a messiah of destruction?