That it was controversial. It has some rape scenes and a lot of violence, but even with all that it still makes you love the guy portrayed as the 'bad guy' as the movie progresses. It's the most glorious type of mind-fuck. Malcom McDowell is great in it and this film is the definition of a cult-classic film. It's a masterpiece. Such a clever artistic vision by Kubrick (the director of 2001, The Shining, Dr Strangelove) , and would still to this day call it ahead of our time. It's fucking art man.
Violence? It has ULTRAVIOLENCE!
Sorry- it needed said. ;)
How can you have any pudding if you won't eat your meat?