Both Lord Krishna and Kalki avatar would manifest similar powers. None has seen Lord Krishna in real life. Yet people world over believed in him because of his sermon of Bhagavad Gita and his ability to convince Arjuna to fight the battle of Dharma (righteousness), the Mahabharata.
Lord Krishna advent in proper Yuga to re-establish Dharma whereas Lord Kalki would advent in present times (almost within a decade from now) to re-establish Dharma (righteousness)! Purpose of both these avatars remains the same.
In times of extreme adversity, strife anyone from masses can don the mantle of an avatar. Every avatar is born an ordinary mortal yet in a very short time one awakens kundalini shakti fully, becoming a man God. Furthermore, exercising administrative capability of Chanakya, a ruthless crusader of truth an avatar finally succeeds eliminating evil from the society.
Coming of an avatar announces a battle of Mahabharata in making. Precipitation of a Mahabharata in times of an avatar is an absolute must. Only then the society can be cleansed of its ills. Such a feat can never be accomplished by a self realized soul alone. Apart from manifesting jnana wisdom of Bhagavad Gita one should be an apt administrator like Chanakya.
To avoid the system becoming a slave to extreme misery Chanakya got 100 kings killed in one night. Untold countrymen and soldiers would have lost their lives had Chanakya not eliminated these all the time fighting kings. To put a full stop to all the time rivalry at borders, elimination of these kings was an absolute must and Chanakya succeeded in doing so.
As per Lord Krishna in Bhagavad Gita, to uplift Dharma if a few are eliminated then no sin is committed. Lord Krishna was that type of person and so shall be Kalki avatar.