Luca Brasi (1896-1945) is a character in Mario Puzo's novel The Godfather, as well as its 1972 film adaptation (portrayed by Lenny Montana).
In The Godfather, Luca Brasi is one of Don Vito Corleone's personal enforcers. Brasi is portrayed as slow-witted and brutish, but his ruthlessness and his loyalty to Don Corleone means he is both feared and respected. Fluent in Italian and able to handle himself in any fight, Brasi is fiercely loyal to Don Vito. He has a dark reputation among the underworld as a savage killer.

At Connie's wedding, Michael Corleone explains to his then girlfriend Kay Adams, the story of how Don Corleone helped his godson Johnny Fontane. Michael explains that his father went to convince an unnamed bandleader to release Johnny from a personal service contract that was holding back Johnny's singing career. After refusing an offer of $10,000 Don Corleone returned the next day with Luca Brasi and within an hour the bandleader signed a release for a second offer of only $1,000. Luca Brasi had held a gun to the bandleader's head while Don Corleone assured him that either his brains or his signature would be on the release contract.

Shortly before Vito Corleone is shot, Brasi (on Vito Corleone's instructions) intends to draw out rival mobster Virgil Sollozzo and the rest of the Don's enemies. Sollozzo, after promises of friendship and a job offer, rams a knife into Luca's hand, pinning it to the bar as an assassin garrottes him from behind (more than likely because Brasi is wearing a bullet proof vest). A Sicilian message is later sent to the Corleone family: a fish wrapped in Brasi's flak jacket. The meaning is made clear to the Corleones: "Luca Brasi sleeps with the fishes". Sollozzo has Brasi killed as it is the best way of ensuring Vito Corleone's vulnerability.
It is mentioned in the novel and implied in the film that Brasi is perhaps the only man Vito Corleone fears and vice versa. It is also implied that Brasi was created to portray Real life Gambino Mafia Hitman Santo "Sonny Boy" Ricchiettore although truth to that is not for sure certain.
Brasi's talent, it was said, was that he could do a job, or murder all by himself, without confederates, which made a criminal conviction almost impossible. He is also known for killing, in two weeks, six men who attempted to kill Don Corleone. These six deaths ended the famous "Olive Oil War".
Many years before The Godfather opens, Brasi impregnated a young Irish prostitute and later murdered her, but did not stop there; on the day of his daughter's birth, he forced the midwife, under pain of death, to hurl his own daughter into a furnace, an act for which she never forgave herself, describing him as an unholy demon that night.

Another early incident involved Brasi killing off two of Al Capone's henchmen hired to kill Don Corleone. Brasi subdued both of them and tied and gagged them with towels stuffed in their mouths. He then hacked one of them to pieces with an axe. When he went to finish off the other one, he found that the man had gone through a shock convulsion and choked to death on the towel.
Brasi's role as personal enforcer/bodyguard to the Don was later filled by Al Neri. Tom Hagen once said to Michael following the completion of Neri's training, "Well, now you've got your Luca."
 

Peter Clemenza (1890-1957) is a fictional character appearing in Mario Puzo's novel The Godfather and two of the three films based on it.
In his young adulthood, in The Godfather Part II, Clemenza is portrayed by Bruno Kirby. In his later years, he is portrayed by Richard S. Castellano.
Peter Clemenza is one of two caporegimes in the Corleone Family (the other being Salvatore Tessio), ruling over the family's territory in Little Italy. Although he is less intelligent than his friend and counterpart Tessio, he is said to be more brutal and direct in the book. In the film, he may be perceived at first as a fat, dim witted thug, but later on he is shown to be a formidable assassin.

Clemenza became a friend of Vito Corleone after immigrating from Sicily, when Corleone held a package of guns for him to prevent their discovery by the police. A friendly and jovial man, he was known as a storyteller among many of his acquaintances and family members - a trait that endeared him to Vito, who Puzo described as "a listener to storytellers." Clemenza got his start selling stolen goods such as dresses and guns with Vito and Tessio as far back as 1917, and became a key figure in the growing Corleone family. Vito kept him close through the years - even making him godfather to his oldest son Sonny - though this was all to control his brutal and more ambitious tendencies.

Clemenza plays a key role in aiding Michael following the shooting of Vito. He retrains Michael how to fire a gun, walking him through the scenario for assassinating Virgil Sollozzo, and plants the gun prior to the assassination. During the murders of the heads of the five families Clemenza shot Don Stracci and his bodyguard, as well as eliminating Carlo Rizzi, Connie Corleone's husband and Michael's brother-in-law in retaliation for setting up Sonny's assassination.
Clemenza's forces include soldiers Paulie Gatto, Willie Cicci, Al Neri, and Rocco Lampone. He handled many of his men closely, proud of picking Lampone as a caporegime and locating Neri as a successor to Luca Brasi. He could also be cruel with them - when he found out that Gatto had been collaborating with Sollozo, he saw it as a personal betrayal and orchestrated the execution personally.

In Mark Winegardner's novel The Godfather Returns, Clemenza was made an informal advisor to Michael as the family attempted to restructure itself in a more legal manner. He died of a heart attack shortly before 1958, a consequence of his excessive lifestyle - an autopsy revealed his heart was "twice the size of a normal man's." (In the film The Godfather: Part II, Willie Cicci, appears to deny this, stating "that was no heart attack" but no further info is given.) Pete Clemenza was succeeded as caporegime by Frank Pentangeli.

In Puzo's novel The Sicilian, Clemenza is featured in Sicily, where he meets Michael Corleone in order to arrange his safe return to America and also to oversee the safe passage of the novel's lead character, Salvatore Guiliano. In this novel he has an older brother, Domenic Clemenza, who is an old-fashioned and well respected Mafia Don. Neither Clemenza nor Michael Corleone are featured in the film version of the novel, presumably because of copyright restrictions on the Godfather film franchise.