The Casalesi clan, which takes its name from the town of Casal di Principe near Naples, has been described as the successor of the Corleone family, which ruled Sicily in the 1980s.
The bloodthirsty family is thought to have carried out more than 1,000 hits in the past 30 years to establish an iron grip on the area between Naples and Salerno.
However, Francesco Schiavone, the head of the clan, will now spend the rest of his life in prison after being successfully convicted.
Schiavone is nicknamed Sandokan after a popular 1970s television series starring Kabir Bedi.
Over the course of the initial trial and the appeal, five people involved in the case were murdered by the clan, including an interpreter. A judge and two journalists were threatened with death during the hearings.
Raffaello Magi, the presiding judge, said: "Unlike the Neapolitan gangsters who live off cocaine dealing or extortion, the Casalesi exploit every area of economic potential.
They do the dumping of the toxic refuse, they hold the monopoly on the cement market, they control the distribution of essential products. They control elections and they offer protection and market opportunities to businesses."
Any business wanting to open in the area controlled by the clan had to pay them for permission and then buy cement off them to build their buildings. The clan is believed to have built parts of the motorway between Rome and Naples and even the prison at Santa Maria Capua Vetere in which many of its members are now held.
In 1996 and 1997, some £400 million was confiscated from the Casalesi. "This is a sum that would have put any normal company on its knees. But Schiavone continued to prosper. The investigators in Naples estimated a total wealth of around £20 billion," said Mr Saviano.
The Casalesi became so bold that some of its members used to hold meetings in the local police station at San Cipriano d'Aversa. Investigators found the clan had used the station telephone and even snorted cocaine off a policeman's desk. The clan stepped up its killing in the run-up to the final verdict, culminating in the assassination of Michele Orsi, a businessman working in waste disposal with the Casalesi. Orsi, 47 was summoned to a cafe in the main piazza at Casale di Principe on June 2 and gunned down in a hail of 18 bullets.
Just two days beforehand, a 25-year-old woman whose aunt had turned state witness was fired on but not killed. The relatives of two other businessmen cooperating with the authorities had already been eliminated.
Schiavone's brother, Walter, was so enamoured of Tony Montana, the fictional Cuban drug dealer in the 1983 film Scarface, that he recreated a replica of his villa, complete with the curved double staircase from which Montana takes his death dive.
Far from meeting a glorious end, however, Schiavone was arrested in 1999 while trying to jump over his garden wall and his villa has now been turned into a physiotherapy centre for disabled people.