Get the list of lines of some file that does not exist in another

To get whole lines of FILE_1 that do not exist in FILE_2

Which is equivalent to FILE_1 - FILE_2

• Using grep:

  grep -v -x -F -f FILE_2 FILE_1
  

• Using comm

  comm -13 FILE_2 FILE_1
  

• Using comm another method

  comm -23 FILE_1 FILE_2