Hugo Chavez basically opposes everything the US does anywhere in the world. In Latin America, the most prominent example of a policy that he opposes is the US policy of trying to isolate Cuba.
Ever since 1960, soon after Fidel Castro's revolution, the US has imposed a trade embargo on Cuba. The US wants to isolate Cuba both economically and politically as a way of putting pressure on the Castro regime. Chavez is a close ally of Castro and sees Castro as something of a role model because Chavez also wants to bring a socialist system to his country. Because of this, Chavez has opposed the US policy of isolating Cuba. He has done so, for example, by selling oil to Cuba at low prices. In exchange, Cuba sends health care workers to help Venezuela. This is the most prominent example of Chavez opposing US policy in Latin America.