Critical Theory
It was developed by a group of sociologists at " The Frankfurt School" in Germany since 1930s.
(Major scholars are Herbert Marcuse, Walter Benjamin, Max Horkheimer, and Theory Adorno and Jurgen Habermas.)
It stems from the philosophy of Karl Marx.
Later, they are influenced by neo-Marxism as well.
Critial theory is a social theory criticizing and changing society as a whole, in contrast to traditional functionalism oriented only to understanding or explaining it.