The Corleone-Ciccio conflict started as a dispute between the Andolini family and Don Ciccio's clan, culminating in the deaths of Antonio Andolini and his wife and son. It ended in the death of Don Ciccio, killed by Andolini's surviving son Vito Corleone, as an act of revenge.
Michael Corleone thinks that it was Hyman Roth who tried to have him assassinated.
In The Godfather, Sollozzo and the Tattaglia's attempt to assassinate Don Corleone. He is shot several times in the back but survives.
Hyman Roth agrees to the hit. This was done by Michael to give Roth a sense of security and superiority that Michael was wrong about who ordered the hit. Michael then goes to Frankie to reveal that he knows it was actually Roth behind the hit.
Fredo betrayed his brother to rival gangster Hyman Roth, who used him as a pawn in a plot to destroy the Corleone Family. Fredo provided unspecified information on the Corleone family in return for receiving compensation (what kind is never specified) independently of the family.
Paulie has seemingly betrayed Vito—and thus the family—by selling him out. In The Godfather, this kind of betrayal is the worst of all sins.
2. Michael and Vito might have placed some of the blame for Sonny's assassination on Tom. Though it turns out that Carlo Rizzi plotted with Barzini to set Sonny up, Michael and Vito probably believed that Tom didn't do enough to stop Sonny from leaving the safety of the family compound that day to find Carlo.
Killing Carlo
Carlo is another person who probably got what he deserved but it further cemented the fact that Michael sold his soul when he took over the family. Carlo was Connie's abusive husband who sold out Sonny to the rival gangs, resulting in his murder.
Don Philip Tattaglia then arranges a meeting between Brasi and Sollozzo. Sollozzo, not fooled by the ruse, impales Brasi's hand into a table while one of his men strangles Brasi to death with piano wire.
Roth secretly plans to assassinate Michael, partly to avenge Moe Greene's murder (as depicted in The Godfather). Roth instructs Ola to befriend Michael's brother Fredo, who provides Ola (and Roth) information about Michael that enables them to make an attempt on his life.
We know Fredo betrayed Michael by working with Hyman Roth and Johnny Ola. What exactly did he do though? He says he didn't know it was going to be a hit and that he was only trying to help the family.
Orson Welles - Don Vito Corleone, The Godfather (1972)
Marlon Brando was always Francis Ford Coppola's first choice for the role of Don Vito Corleone.
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.
During the meeting, Sonny expresses interest in the deal; after the meeting, Vito chastens his son for letting an outsider know what he was thinking. Shortly afterward, as Vito goes to buy oranges from a fruit stand, Sollozzo's hitmen emerge with guns drawn. Vito runs for his Cadillac, but is shot five times.
1 Don Vito Corleone - 'The Godfather' (1972)
Don Vito Corleone (Marlon Brando) went from being a penniless-orphaned immigrant to becoming one of the country's most powerful and respected mafia bosses.
In Winegardner's 2006 sequel, The Godfather's Revenge, Fredo appears in one of Michael's dreams. In the dream, Fredo warns Michael about an unspecified threat, and asks him why he had his own brother killed. Much of the novel portrays Michael dealing with his guilt over Fredo's murder.
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. After Michael returns from Sicily, he assumes Sonny's place as Vito's heir apparent.
Shortly afterward, Vito's chief rival, Don Emilio Barzini, bribes Gatto to betray the Corleone family by giving him the information his men need to stage an assassination attempt on Vito. On the day the hit went down Gatto calls in sick, leaving only Fredo to protect the Don. Vito is seriously wounded in the attempt.
Connie (who was unaware of her husband's role in Sonny's murder), hysterical after Carlo's death, blames Michael, denouncing him in front of his wife, Kay.
She married him at a lavish old-style Sicilian ceremony in 1945. Carlo and Connie agreed to the ceremony due to her father's displeasure in her choice of groom (he was not only a hoodlum, but half-northern Italian). They moved into an apartment in Hell's Kitchen.
He died at the age of thirty-one, two months short of his thirty-second birthday. Sonny's death comes as a shock to Michael who was devastated upon hearing the news in Sicily. Vito was told the news by a saddened Tom Hagen, who had to have a drink before being able to tell him.
Clemenza's strongest attribute to the Corleones was his stubborn loyalty, not his intelligence. Thus, regardless of his complaints about Michael, he would never have betrayed the Corleones. Clemenza was known as a superb judge of talent.
A rat is another word for snitch or informant. These four rats betrayed the Corleone family: Salvatore “Sal” Tessio, Paulie Gatto, Fabrizio and Carlo Rizzi.
In the novel, Greene is murdered shortly afterward by Al Neri. At the end of the film, Michael has Greene killed as part of his slaughter of the Corleone family's enemies.