I did a pole in my Journalism class on which movie was the "saddest".
There were three movies to chose from, The fault In Our Stars, Titanic, or the Boy In The Stripped Pajamas.
The Boy In The Stripped Pajamas won by a landslid. This movie is based on the holocaust. Where a rich family moved closer to a concentration camp because their father was head Sargent in control of the camps. He had a young son who explored his new home, and found a little boy deep in his back yard, who seemed to always wear "pajamas".
Really, this little boy was in uniform for the concentration camp. But the rich boy had no idea, he thought he made a new friend and could meet him any time he wanted and talk to him through a fence. The rich boy thought he had a new friend, and they would play through a fence that separated them everyday.
The boys saw each other everyday, they talked, played catch and didn't have a care in the world.  One day, a problem occurred and the rich boy couldn't find his friend so he went over the fence to look for him.
That's all i'm going to explain, because I don't want to spoil the ending. But this is a very recommended movie!