Sub macro()
Set ws2 = Sheets("Sheet2")
lr = ws2.Cells(Rows.Count, 3).End(xlUp).Row
Set Rng = ws2.Range(Range("C2"), ws2.Range("C" & Rows.Count).End(xlUp))
Set dict = CreateObject("Scripting.Dictionary")
For Each c In Rng
dict(c.Value) = ""
Next
arrKeys = dict.Keys
res = Join(arrKeys, ",")
Sheets("Sheet1").Range("A1") = res
End Sub