Karl Marx's basic philosophy was very much opposed to that of Adam Smith, whom you asked about a bit ago. Where Smith believed the government should let the markets do what they wanted to, Marx believed that the market economy was a bad thing and should be gotten rid of.
Marx believed that capitalism was a system that oppressed the workers. He believed that everything about capitalism was intended to help the upper classes (those who owned the "means of production") and to harm the lower classes (the ones who had to use the means of production to work with. Marx believed that the two classes would be in conflict with one another until, eventually, the lower classes would overthrow the upper classes and create a society ruled by the workers. Then, there would be no more government and no more private property so no one could exploit anything else. Marx, then, wanted to destroy the market economy because he saw it as a way of oppressing the workers.