I can't remove this category myself as admins have long locked the page due to its history of edit-wars but Alan Yates from Cannibal Holocaust is not, contrary to popular belief, a true "Complete" Monster because he has ONE saving grace in the film.
When Alan's plan goes horrifically wrong he shows geniune love for his girlfriend and was willing to abandon the entire project to save her, it was Mark that convinced Alan to continue.. if not for Mark Alan would very likely of died trying to save his girlfriend and that, despite his infinite flaws, is a saving grace.
Let's also take into account Alan has an entire group of friends, not to mention a girlfriend, could the inhuman madman you guys talk of truly be able to make these many friends and a romantic relationship if he was devoid of ALL humanity?
in fact to have any romantic feeling is to show a very basic empathy / connection to something other than oneself, a trait that CMS can never have.
Alan Yates was a horrible guy but he was no "Complete" Monster as he had some human traits, those human traits are what made him all the more disturbing.