“For in Him dwelleth all the fulness of the Godhead bodily. And ye are complete in Him, which is the head of all principality and power:”
In who? In Christ is the fulness of the Godhead.
How is that?
23 “Behold, a virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us.”
We all know this virgin is Mary and this prophecy documents the birth of Christ who is referenced as “Emmanuel” which simply means, “God with us,” (Isaiah 7:14).
Christ was “God with us” on earth in the flesh and the Spirit was certainly with Him. This is how you have the fulness of the Godhead.
Take note our Father is the head of all “principality and power“. This would be on earth and Heaven above. While Satan has reign on earth, our Father still has the ultimate authority.
This verse does not designate the complete ownership of the kingdoms of the earth to God however. We know “the kingdoms of this world are become the kingdoms of our LORD, and of His Christ” at the end of the Seventh Trumpet and not until then (Revelation 11:15).