Option Explicit

Sub exists50()
Dim x
Dim ar50&(0 To 50)
Dim i&, r&, c&, g&: g = 0
Dim arRes&(1 To 100000, 1 To 1)
Dim exists As Boolean: exists = False

For i = 0 To 50
      ar50(i) = i
Next

x = Range("A1:E" & [a65535].End(xlUp).Row)

For i = 0 To 50
exists = False
      For r = 1 To UBound(x)
          For c = 1 To 5
              If x(r, c) = ar50(i) Then
                  exists = True
              End If
          Next
      Next
      If exists = False Then
      g = g + 1
          arRes(g, 1) = ar50(i)
      End If
Next
If g = 0 Then Exit Sub
[g1].Resize(g) = arRes
End Sub

Public Sub www()
     Dim a, v, b(0 To 50, 1 To 1), i&, n&
     a = [a1].CurrentRegion: [g1].CurrentRegion.ClearContents
     With CreateObject("scripting.dictionary")
         For Each v In a
             .Item(v) = ""
         Next
         For i = 0 To 50
             If .exists(i) Then Else b(n, 1) = i: n = n + 1
         Next
     End With
     [g1].Resize(n + 1) = b
End Sub

Public Sub www1()
     Dim a, j&, b(0 To 50, 1 To 1), i&, n&, m&, f As Boolean
     a = [a1].CurrentRegion: f = -1
     [h1].CurrentRegion.ClearContents
     On Error Resume Next
     With Application
         For j = 0 To 50
             For i = 1 To UBound(a, 2)
                 m = .Match(j, .Index(a, 0, i), 0)
                 If Err Then Err.Clear Else f = 0: Exit For
             Next
             If f Then b(n, 1) = j: n = n + 1
             f = -1
         Next
     End With
     [h1].Resize(n + 1) = b
End Sub

Public Sub www2()
     Dim j&, b(0 To 50, 1 To 1), n&, rng As Range
     Set rng = [a1].CurrentRegion
     [h1].CurrentRegion.ClearContents
     For j = 0 To 50
         If Application.CountIf(rng, j) = 0 Then b(n, 1) = j: n = n + 1
     Next
     [h1].Resize(n + 1) = b
End Sub

Sub test()
     Dim a(0 To 50) As Boolean, rng As Range, c As Range, i&
     Set rng = [a1].CurrentRegion
     For Each c In rng.Cells
         a(c.Value) = True
     Next
     Set rng = [g1].CurrentRegion
     rng.ClearContents
     For i = 0 To 50
         If Not a(i) Then
             rng.Cells(1, 1) = i
             Set rng = rng.Offset(1)
         End If
     Next
End Sub