Which uncle of Tony is a rival in the DiMeo family?

Tony Soprano's rival uncle in the DiMeo family is Corrado “Junior” Soprano.

Usually called Junior or “Uncle Jun,” Corrado John Soprano Jr. is Tony's paternal uncle: his younger brother Johnny Soprano was Tony's father. Junior is played by Dominic Chianese and becomes one of the most important power figures in The Sopranos. He is old-fashioned, proud, intelligent, and deeply sensitive to the possibility that younger men no longer respect him.

After acting boss Jackie Aprile Sr. dies, Junior and Tony compete for control of the DiMeo crime family. Tony publicly supports Junior's elevation to boss, while secretly arranging matters so that Tony retains real influence. Junior's resentment and suspicion eventually contribute to attempts against Tony, turning a family disagreement into a dangerous leadership struggle.

Although Junior holds the title of boss for part of the series, Tony is effectively the stronger power. Junior later suffers declining influence, legal problems, and mental deterioration. The character's nickname can cause confusion because “Junior” is part of his name, not a reference to Tony being his junior.