Krsna as His original Vrindavana Form, never leaves Vṛndāvana, all His pastimes in the material world, including killing demons, are performed by His Visnu-tattva expansions who play the part of Krsna in the material world.

Srila Prabhupada - "Kṛṣṇa as His original childhood form never leaves Vṛndāvana, all the forms of Kṛṣṇa that appear elsewhere are His Viṣṇu-tattva expansions."(BG, As It Is Ch 10 text 37)

Srila Prabhupada - "The original Lord Kṛṣṇa never leaves Goloka Vṛndāvana. All the plenary expansions are one and the same Viṣṇu-tattva however, there is no difference in Their potency." (SB, Canto 3 Ch 1 Text 34)

Krsna is likened to the original candle that lights all other candles of the same luminosity.

Kṛṣṇa first expands Himself as Balarāma (His older brother in Vṛndāvana Lila) and from Balarama, all Visnu-tattva expansions manifest on the Vaikuntha planets.

Krsna's four armed Visnu-tattva expansion plays the two-armed Krsna outside of the spiritual world within the material world and kills many demons. Such killing of demons does not happen in the original Vṛndāvana in the spiritual world, it only happens in the facsimile Vṛndāvana in the material world. 

All Visnu-tattva/Narayana expansion do not have those four extra qualities Krsna has always, therefore, Krsna is always the Supreme Personality of Godhead and cause of all causes and expands Himself into innumerable categories of living entities - 

Visnu-tattva (Balarama, Visnu, Narayana, Maha-Visnu, Garbhodakashayi Visnu, Paramatma etc), 

Visnu-"sakti"-tattva (Radharani and Her associates known as the internal energy), 

Siva-tattva (Siva and his expansions), 

Jiva-tattva (the eternal individual jiva-souls known as the marginal living entities)

Of all the living entities, the ones who are almost equal to Krsna are called Visnu-tattva (Balarama, Maha-Visnu, Garbhodakashayi Visnu, Paramatma etc),  and Visnu-"sakti"-tattva (Radharani and Her eternal unlimited associates)

While other living entities, the marginal living entities (jiva-souls), are "separated individual beings" being independent from Krsna's absolute control due to having the freedom will to voluntarily provide their own unique contributions in the way they choose in their relationship with Krsna, or even reject Him if they choose. 

Ultimately such independent contributions or service by the individual jiva-souls deepens, expands and personalises one's relationship with Krsna. 

This allows individual unique voluntary loving expressions, exchanges and reciprocation with Krsna to always exist in a "two-way" healthy exchange of loving feelings. 

The eternal individual jiva-souls can always express their independent free will separate from Krsna, for the purpose of allowing them to voluntarily thoughtfully contribute to the relationship making it a "two-way" exchange of loving reciprocation, co-operation and personal contributions.

Denying personal individual contributions or offerings, only extinguishes all personal voluntary independent contributions from the individual jiva-souls, resulting in the destruction of their unique individuality and character leaving only impersonalism.

Srila Prabhupada - "In the spiritual world service to Krsna is always voluntary, some devotees serve as a flower, and can change to unlimited forms, that is spiritual life, always voluntary, one can serve as human form, as cow, calf, flower, as plant, as water, it is inconceivable." (SB, Melb, May 20, 1975)

The individual jiva-souls have their own unique independent personality, character and identity separate from Krsna's Personality, this allows the jiva-souls to express themselves independently from Krsna, allowing voluntary personal contributions or unique offerings, that enrich and expand loving cooperation, reciprocation and exchanges between Kṛṣṇa and the individual jiva-souls.  

The individual jiva-souls in the spiritual world always have their own unique ability of independent self expression, allowing them to voluntarily contribute in their own unique way in a "two-way" exchange of creative offerings where the individual jiva-souls thinks for themselves and never told how to think or what to contribute.

Srila Prabhupada – “The impersonalist philosophy is oneness so how there be love with just one? Is it possible? Have you got any such experience that love means one? No. Love means two. There must be two, the lover and the beloved. Kṛṣṇa is already lover. He loves you so much that He's trying to get you back. That is Kṛṣṇa's attempt. "Please, My dear boy, or My dear friend, My dear servant.” (Lecture SB, Canto 2 Paris, June 12, 1974)

The individual jiva-souls in the spiritual world are independent thinking PERSON, as an eternal spiritual bodily form who have the freedom to express themselves in their own unique way, the way they choose, by voluntarily serving Radha and Krsna without being forced in anyway as Prabhupada explains here.

Srila Prabhupada – “Love is reciprocal, voluntary, good exchange of feeling, then there is love. It never achieved by force, no, Krsna does not want to become a lover like that - ‘You love me, otherwise I shall kill you!” (Lecture, Washington DC July 8, 1976)

In the spiritual world Maya or the material energy does not exist, so the individual jiva-souls can never be tempted by Maya or material energy on the Vaikuntha planets, or in Krsna's central Abode of Goloka Vrindavana however, what does eternally exist in the spiritual world is free will (self-expression) which is also the only cause of fall down from the Vaikuntha planets and Goloka-Vrindavana (free will)

As explained above, Lord Siva (Siva-tattva), is neither Visnu-tattva or jiva-tattva (jiva-soul) but is in a league of his own with his followers, he is very merciful to the degraded extremely fallen jiva-souls who have become ghostly persons (frustratingly existing without a gross material bodily vessel)

All the different categories of living beings are Krsna's expansions, each having a portion of His 64 qualities however, only Kṛṣṇa has all 64 qualities in full all the time all the time.

Visnu-tattva expansions have 60 of Krsna's 64 qualities which is 93.75%. 

Siva-tattva expansion has 55 of Krsna's 64 qualities which is 85.938%

Jiva-tattvas (jiva-souls) expansions have 50 of Krsna's 64 qualities which is 78.125%.

Being all-powerful and the cause of all causes, Krsna can expand Himself into unlimited Forms with the same power and characteristics He possesses, without diminishing Himself in anyway.

So to be clear, Krsna as His original eternal childhood infinite Form, never leaves Goloka-Vṛndāvana, therefore it is His Visnu-tattva expansions who enter the material world and plays the role of the original Kṛṣṇa in the earthly Vṛndāvana dham facsimile as seen in paintings below.<=>