John M. "Cockeye" Dunn (August 24, 1910 – July 7, 1949 Ossining, New York) was a New York mobster involved in the numbers racket and labor racketeering as a top enforcer for his brother-in-law Eddie McGrath.
 He was convicted together with Andrew "Squint" Sheridan of the 1947 murder of Greenwich Village hiring stevedore Anthony "Andy" Hintz, and executed by electric chair on July 7, 1949, aged 38.
Vito "Don Vitone" Genovese (November 27, 1897 – February 14, 1969) was an Italian-American mobster who rose to power during Prohibition as an enforcer in the American Mafia.
 A long time associate of Charles Luciano, Genovese took part in the Castellammarese War and helped shape the rise of the Mafia and organized crime in the United States.
 He would later lead Luciano's crime family, which was renamed the Genovese crime family, for 12 years.
Abraham "Whitey" Friedman (c. 1897 – April 25, 1939) was a New York mobster and former associate of Nathan "Kid Dropper" Kaplan and later for labor racketeers Louis "Lepke" Buchalter and Jacob "Gurrah" Shapiro as an enforcer in New York's garment district during the 1920s and 1930s.
 One of many former associates killed by Murder, Inc. on the orders of Buchalter, he had recently been called in for questioning by investigators with crusading District Attorney Thomas E. Dewey and gunned down in a drive by as he was walking near his home on East 96th Street during the early evening of April 25, 1937, (although other sources state 1935).
 Before his murder, Friedman was suspected of informing on Buchalter.
Primo Cassarino (born April 26, 1956 Dyker Heights, Brooklyn) is a New York mobster who became an enforcer for Gambino crime family, and extorted money from actor Steven Seagal.
Vincent Louis Gigante ( ; March 29, 1928 – December 19, 2005), also known as "Chin", was a New York Italian-American mobster in the American Mafia who was boss of the Genovese crime family from 1981 to 2005.
 Gigante started out as a professional boxer who fought 25 bouts between 1944 and 1947.
 He then started working as a Mafia enforcer for what was then the Luciano crime family.
 Gigante was one of five brothers: Mario, Pasquale, Ralph and he all became mobsters in the Luciano family, forerunner of the Genovese family.
 Only one brother, Louis, stayed out of the crime family, instead becoming a priest.
 Gigante was the shooter in the failed assassination of longtime Luciano boss Frank Costello in 1957.
 After sharing a prison cell with Costello's rival, Vito Genovese, following Vito's conviction for heroin trafficking, Gigante became a caporegime, overseeing his own crew of Genovese soldiers and associates that operated out of Greenwich Village.
 Gigante was one of Genovese's most loyal supporters, siding with him throughout the struggle for power with Costello.
Alphonse "Little Al" D'Arco (born July 28, 1932), also known as "The Professor", is a New York mobster who became the acting boss of the Lucchese crime family.
 He was the first boss, acting or otherwise, of a New York crime family to become a government witness.
Anthony Salvatore "Gaspipe" Casso (born May 21, 1940 in Brooklyn, New York City) is an Italian-American mobster and former underboss of the Lucchese crime family.
 During his career in organized crime, Casso was regarded as a "homicidal maniac" in the American Mafia, single-handedly killing over 40 to 50 people, and ordering as many as 100 or more murders.
 Former Lucchese captain and government witness Anthony Accetturo once said of Casso, "all he wanted to do is kill, kill, get what you can, even if you didn't earn it."
 In interviews and on the witness stand, Casso has confessed involvement in the murders of Frank DeCicco, Roy DeMeo, and Vladimir Reznikov.
 Casso has also admitted to several attempts to murder Gambino family boss John Gotti.
The Valachi Papers is a biography written by Peter Maas, telling the true story of former mafia member Joe Valachi, a low-ranking member of the New York-based Genovese crime family, who was the first ever government witness coming from the American Mafia itself.
 His account of his criminal past revealed many previously unknown details of the Mafia.
 The book was made into a film ("The Valachi Papers"), released in 1972, starring Charles Bronson as Valachi.
Manfredi "Al" or "Alfred" Mineo (] ) (1880 – November 5, 1930) was a Brooklyn-based New York mobster, who headed a strong American Mafia crime family during the Castellammarese War.
 Mineo's organization would eventually become the present-day Gambino crime family.
Peter LaTempa (1904 - January 15, 1945) was a New York mobster and associate of the Genovese crime family, who later agreed to become a government witness against Vito Genovese.

Question: New York mobster, Peter LaTempa became a witness against what enforcer in the American Mafia?
Answer: Vito Genovese