Thanks for your help. In the end I found a solution by duplicating the same code. It looks like below. It's ugly and slow but it works somehow lmao.
Maybe someone can refactor it.
Dim LR As Long, i As Long
LR = Range("A" & Rows.Count).End(xlUp).Row
For i = LR To 1 Step -1
If WorksheetFunction.CountIf(Columns("A"), Range("A" & i).Value) > 1 Then Range("A" & i).ClearContents
Next i
Dim sh As Worksheet
Dim LstRw As Long, x
Set sh = Sheets("Sheet1")
With sh
LstRw = .Cells(.Rows.Count, "A").End(xlUp).Row
For x = LstRw To 2 Step -1
If .Cells(x, 1) Like "*[ab]*" Then
.Cells(x, 1).EntireRow.Resize(2).Insert
End If
Next x
End With
Dim LRD As Long, q As Long
LRD = Range("C" & Rows.Count).End(xlUp).Row
For q = LRD To 2 Step -1
If WorksheetFunction.CountIf(Columns("C"), Range("C" & q).Value) > 1 Then Range("C" & q).ClearContents
Next q
Dim sh2 As Worksheet
Dim LstRw2 As Long, w
Set sh2 = Sheets("Sheet1")
With sh2
LstRw = .Cells(.Rows.Count, "C").End(xlUp).Row
For w = LstRw To 1 Step -2
If .Cells(w, 1) Like "*[ab]*" Then
Debug.Assert True
'.Cells(w, 1).EntireRow.Resize(1).Insert
End If
Next w
End With