Nicolas was born in the Bronx and his father was a respected Mafia member. At age eight, Nicky's Aunt Mo told him to kill his parents and his younger sister- framing his uncle for the killings so that she could take over the family's criminal operations. Mo adopted Nicky, regularly forcing him to have sex with her. The psychological trauma turned him into even more of a psychotic sadist, leading to his eventual murder of Aunt Mo- suffocating her with a pillow during intercourse.
He was later employed by Don Cesare and ordered to intimidate a Japanese crime boss, David Kai. They dined and Kai refused his offer. Cavella revealed that the meat in Kai's dish was his youngest son, then killed the elder two but left Kai alive. The action made him a pariah, and he was exiled to Boston with his underlings Pittsy and Ink. In Boston he ran drugs for fifteen years during which time he engaged in a relationship with corrupt intelligence agent Rawlins.
When the Punisher almost exterminated the Mafia leadership in New York, mob boss Larry Barrucci called in Cavella to help stabilize the situation. Nicky agreed to kill the Punisher, who at that time was being held in a hotel room by Microchip working along with the CIA in order to coerce Castle into working with the government as a counter-terrorism agent. Pittsy castrated Agent Roth to find the location. Cavella, Pittsy, and Ink went in, killing and wounding multiple agents. Pittsy was shot in his shoulder and Ink was killed by O'Brien. Micro and Frank escaped to one of his safehouses and Cavella sent an army of Mafiosos after them. While the Punisher and Microchip were distracted by the frontal attack, Pittsy snuck into the building. Seriously wounding Micro and engaging Frank in a brutal fight, Pittsy was eventually thrown out a window and impaled on a gate below. Cavella forced Barrucci to attack the Punisher himself, and fled as Castle killed the man. Frank was about to shoot Nicky in the back but was interrupted by a dying Pittsy, whom he shot in the face and finally killed. Cavella killed two cops nearby and escaped in their car.
Two years later, he remained one of the few criminals to survive an encounter with the Punisher. He and Teresa Gazzera, Pittsy's sister, desecrated the Castle family graves, exhuming and urinating on the remains. Taking advantage of the leaderless Mafia, he was able to get himself elected Don. The Punisher went on a rampage, massacring local gangs. Rawlins was assigned by the CIA to kill Frank Castle in an attempt to cover up a previous operation, and he joined with Cavella. Their plan was for Cavella to sit out in the open as bait, and for Rawlins to kill Castle with a sniper rifle when the Punisher showed himself. The plan failed because O'Brien returned, hunting Rawlins for her own reasons. She kidnapped him and engaged Cavella's minions, allowing Frank to escape with her. Cavella and Teresa followed their car to Roth's apartment, where Rawlins was being interrogated on camera by Castle. Teresa tried to seduce Nicky while waiting in the vehicle but he disgustedly pushed her away. Angered, she broke into the apartment and attacked the sleeping Castle and O'Brien, wounding Frank but getting killed in the process. Rawlins kills Roth and escapes.
The next day, Castle and O'Brien track down Cavella, who takes a young boy hostage. Castle warns him that if he hurts the boy he'll suffer a painful death and confronts Cavella on his cowardice. Nicky surrenders himself, letting the boy go. He's put in the luggage booth and driven deep into the forest. Frank shoots him in the belly while explaining him how he'll die. Hunters found his corpse later, with his eyes pecked out by birds.