Sub UNIQUE()
Dim ws1 As Worksheet: Set ws1 = Sheets("Sheet1")
Dim ws2 As Worksheet: Set ws2 = Sheets("Sheet2")
Dim ws3 As Worksheet: Set ws3 = Sheets("Sheet3")
Dim res As Range: Set res = ws3.Range("A2")
Dim r1 As Range: Set r1 = ws1.Range("A2:B" & ws1.Range("A" & Rows.Count).End(xlUp).Row)
Dim r2 As Range: Set r2 = ws2.Range("A2:B" & ws2.Range("A" & Rows.Count).End(xlUp).Row)
Dim ar1() As Variant: ar1 = r1.Value
Dim ar2() As Variant: ar2 = r2.Value
Dim SD As Object: Set SD = CreateObject("Scripting.Dictionary")
Dim tmp As String
For i = 1 To UBound(ar1)
tmp = Join(Array(ar1(i, 1), ar1(i, 2)), "-")
If Not SD.exists(tmp) Then SD.Add tmp, Nothing
Next i
For j = 1 To UBound(ar2)
tmp = Join(Array(ar2(j, 1), ar2(j, 2)), "-")
If Not SD.exists(tmp) Then SD.Add tmp, Nothing
Next j
ws3.Range("A1:B1").Value = Array("ID", "Absent")
Set res = res.Resize(SD.Count, 1)
res.Value = Application.Transpose(SD.keys)
res.TextToColumns Destination:=res, DataType:=xlDelimited, Other:=True, OtherChar:="-"
End Sub