Macro to Delete "duplicate" col W

try this instead:

Sub Delete_Duplicates_ColW()
    With Sheets("imported Data")
        .Range("$A$5").AutoFilter Field:=23, Criteria1:="Duplicate"
        .AutoFilter.Range.Offset(1, 0).Rows.SpecialCells(xlCellTypeVisible).Delete (xlShiftUp)
        .AutoFilterMode = False
   End With
End Sub

With Cells(5, 1).CurrentRegion.Columns(23)
    .Value = Evaluate("=IF(" & .Address & "=""Duplicate"",1," & .Address & ")")
    .SpecialCells(xlCellTypeConstants, xlNumbers).EntireRow.Delete
End With