Most noteworthy, the novel depicts Clemenza's fatal heart attack (mentioned in The Godfather Part II), and the many conspiracy theories that he had actually been murdered by the Rosato Brothers, former Corleone soldiers who had formed their own gang after a dispute over the future of the family.
In The Godfather, Part II, Fredo Corleone makes a comment about Clemenza, who had taken over the leadership of the New York area for the Corleone Family, dying of a heart attack.
As Vito rose to prominence in the Mafia underworld, Tessio and Clemenza rose with him, each eventually settling into the Caporegime roles. However, Vito informed the two men not to meet together socially, telling them it was a security precaution.
While Tom Hagen initially suspected Clemenza of being the one who would betray Michael to Don Emilio Barzini's alliance, Michael reasoned that the more cunning Tessio was the culprit. Clemenza's strongest attribute to the Corleones was his stubborn loyalty, not his intelligence.
In the sequel novel The Godfather's Revenge, Hagen is murdered in 1964 by traitorous Corleone henchman Nick Geraci, who ties him up in a car that he sinks into a swamp.
Michael arranges to have Roth killed at the airport where he is about to be taken into U.S. federal custody. Minutes after disembarking the plane, he is fatally shot by Michael's caporegime Rocco Lampone, posing as a reporter. Rocco himself is killed by federal agents as he tries to escape.
He is also mentioned many times throughout the film; the dialogue makes it clear that Michael is tormented with guilt over ordering his brother's death, and that it has alienated him from his ex-wife, Kay (Diane Keaton), and his son, Anthony (Franc D'Ambrosio), both of whom know the truth about Fredo's death.
Most noteworthy, the novel depicts Clemenza's fatal heart attack (mentioned in The Godfather Part II), and the many conspiracy theories that he had actually been murdered by the Rosato Brothers, former Corleone soldiers who had formed their own gang after a dispute over the future of the family.
Fredo was aware that Hyman was angry with Michael's aggressiveness in Las Vegas, and he simply allowed Hyman to attempt to kill Michael so that he could hopefully claim the title of Don Corleone. Of course, we all know how it eventually ended up going down.
Having Paulie brought to the Corleone compound Sonny Corleone deduced that Gatto had sold out his father. Sonny ordered Clemenza to have Gatto killed as soon as possible, saying he did not want to see Gatto again.
During the meeting, Sonny, the family underboss, expresses interest in the deal, but Vito refuses the offer as he finds narcotics too much of a "dirty business". Barzini then approves Sollozzo's plan to have Vito murdered in the hopes that Sonny, as his father's successor, will accept the deal.
Enraged, Sonny speeds towards Connie's apartment in Hell's Kitchen ahead of his bodyguards. At the Long Beach Causeway toll plaza, Barzini's men trap Sonny and shoot him to death. During a meeting with the other crime family dons to establish peace, Vito realizes that Barzini masterminded Sonny's murder.
Ultimately, Tessio betrays Michael by helping arrange his assassination at a peace summit with Barzini and Philip Tattaglia. The summit will be held in Tessio's fiefdom in Brooklyn, where Michael will presumably be safe. In return, Tessio was to inherit the Corleone family upon Michael's death.
A rift grows between Pentangeli and Michael, however, that eventually results in Pentangeli betraying the family. Pentangeli's character was created in The Godfather Part II by Coppola and Puzo due to actor Richard Castellano not reprising his role as Clemenza in the sequel.
Vito warns Michael that Barzini will set Michael up to be killed under the guise of a meeting; Barzini will use one of the Corleone family's most trusted members as an intermediary. Shortly afterwards, on July 29, 1955, Vito dies of a heart attack in his garden while playing with his grandson, Michael's son Anthony.
At the end of the film, Michael has Greene killed as part of his slaughter of the Corleone family's enemies. Neri surprises Greene while he is getting a massage and shoots him through the eye. This allows Greene's casinos to become property of the Corleone family.
As Fredo prays the Hail Mary (which he claimed brought him luck whilst fishing), Neri shoots him in the back of the head, not knowing that Anthony was watching from his bedroom window.
Eventually, Tattaglia suffered the same fate as his fellow conspirators; he was in bed with a prostitute in a motel room despite being married when Rocco Lampone and another man (in the video game, that is Aldo Trapani), acting on the orders of Michael Corleone, burst in and riddled Tattaglia with machine gun fire.
Fredo's decision is most likely a result of resentment toward Michael, by whom he felt he had been passed over. Michael was Fredo's "kid brother," and the fact that their father chose for Michael to take over the "family business" came as a great insult to Fredo, who was neither as intelligent nor as strong.
He did not care who he angered, as long as he was feared, and he deliberately cultured such a fearsome reputation that even the top crime boss of New York, Giuseppe Mariposa, was afraid of directly retaliating against Brasi for buying his stolen alcohol shipments, to the point where Mariposa demanded that the Corleone ...
In the late summer of 1948, Sonny Corleone was lured into a trap and was killed at the Jones Beach Causeway by Barzini family hitmen in order to avenge Carlo. The hit was engineered by Emilio Barzini after Carlo, angered at the loss of his income and at the fact that Sonny had beaten him, helped set it up.
