Not a "Christian" but a believer in the one true and living God. Even Nebuchadnezzar ultimately believed on Yahweh Elohim. It was Cyrus who told the Jews in his empire to return to Jerusalem and to rebuild the Temple.
Key word: ultimately
Cyrus, the leader of the world, didn't believe...
until he did.
Cyrus was used for the transfer of wealth to God's people.
“Thus says the Lord to His anointed,
To Cyrus, whose right hand I have held—
To subdue nations before him
And loose the armor of kings,
To open before him the double doors,
So that the gates will not be shut:
2 ‘I will go before you
And make the crooked places straight;
I will break in pieces the gates of bronze
And cut the bars of iron.
3 I will give you the treasures of darkness
And hidden riches of secret places,
That you may know that I, the Lord,
Who call
you by your name,
Am the God of Israel.
4 For Jacob My servant’s sake,
And Israel My elect,
I have even called you by your name;
I have named you,
though you have not known Me.
Isaiah 45:1-4