Vito Corleone is a composite of several real-life Mafia Dons:
--In the novel, he defeats a rival whom he arranges to kill at a restaurant and who dies with a mouthful of bread. The dead gangster would be Joe The Boss Masseria, which would make Vito's character like Masseria's nemesis: Salvatore Maranzano, who won the Castellemmarese War of 1930-31.
--Vito's "the biggest importer of olive oil in the U.S." That makes his character like Joe Profaci, who was the biggest importer of olive oil in the U.S. (his family eventually became the Colombos).
--Vito has two capos, one who remains loyal (Clemenza), one who betrays his son (Tessio). That makes Vito like Joe Bonanno, whose capo, Frank Labruzzo, stayed loyal, and whose other capo, Gaspar DiGregorio, betrayed Joe and his son, Salvatore ("Bill").
--But the one Don whom Vito most resembles is Frank Costello, called "the chairman of the board" because of his pre-eminence among Mafiosi. Costello also was the biggest in gambling, and "had all the judges in New York in his pocket." He also retired after an unsuccessful attempt on his life.