The nihilistic art movement which declared that values has been rendered meaningless by the horror of world war i was

I would contend that the right answer is Dada.

Explanation: Just to elaborate a little on the answer, it can be added that Dada or Dadaism was an art movement that started in Zurich, Switzerland, during World War I. Its founder was the writer Hugo Ball. Dada artists produced a wide variety of works, often of a satirical and meaningless nature, in response to the horrors and the stupidity of the conflict. Their goal was to show to the world that established values—social, moral, artistic—were no longer valid. In order to do that, they challenged the art establishment, and some of them, like Duchamp, exhibited everyday objects as works of art. Dada became an international movement and it influenced other subsequent movements, such as Surrealism.  

e                   for effort