After the arrival of Killabilly into the world of Earth, Killabilly waits for Juliet in hostile rampage. On a dark night in the city of San Romero, it slowly begins to crumble, as large orange buildings and gravel roads get destroyed, as Juliet races towards Killabilly. Various vehicles are also apparent through the long road that also get easily destroyed throughout the process. A few zombies also rise from the ground of the road as well as Juliet is making her way through Killabilly. When Killabilly is defeated, San Romero is nearly completely destroyed.
When Juliet manages to retrieve the inside of Killabilly's body, a large, fleshy, pink, tunnel is set to lead to Killabilly's large, unhealthy Heart where Swan's decapitated corpse lies. Tentacle-like appendages are also apparent in Killabilly's body, presumably acting as immune system to prevent foreign bodies from attacking.
During Juliet's journey to confront Killabilly, buildings and roads begin to crumble, as well as various vehicles that either lie on the road or are thrown.
When Juliet is thrown on the stage of area, Killabilly will cause further destruction to construct harm towards Juliet. Such things are: The tossing of various vehicles, zombies and helicopters.
When Juliet jumps on the arm of Killabilly, her father Gideon sacrifices himself causing a large hole on Killabilly's face for Juliet to jump in and completely destroy him. Once inside tentacle-like appendages will attack Juliet, in which she must destroy in order to progress.
The Boss Fight begins, when Juliet finally reaches Killabilly, only to be grasped and held, while Killabilly prepares to harm her. With her Chainsaw only good for close ranged use, she uses her Chainsaw Blaster in order to irritate the face of Killabilly. Juliet can use her Chainsaw to move Killabilly's arm in order to evade long ranged or close ranged attacks. Killabilly will flick and spit zombies at Juliet, with the assistance of flying zombies, coming to his aid. Once Killabilly is weakened, Killabilly will attempt to swallow Juliet (replacing finishing strikes), but will later spit her out when Juliet begins to chop the inside of his mouth.
Now on a rubble platform, Killabilly is now less of a danger to Juliet, but is now more difficult to inflict damage as his distance prevents Juliet from doing any serious harm in a usual amount of time. Killabilly will at times move back to do Guitar Swings that cause vehicles and various other zombies to fly unto the platform to attack Juliet. He will also magically teleport various other vehicles along with prepared zombies to attack Juliet. His claws are the only vulnerable part of his body that Juliet can inflict true harm to. Once weakened, Killabilly will try to strike Juliet with his claws, in which Juliet cuts off. She will then jump on his arm and begin to struggle getting inside his body.
When Juliet finally reaches the inside of Killabilly's body, Juliet must walk through a tunnel filled with flesh and tentacles. These tentacle-like appendages will begin to attack Juliet when she has reached far enough into the tunnel, creating a QTE. Once they have reached Killabilly's heart, Juliet is informed that the only way Killabilly can be defeated is if a Nick Bomb was established in order to defeat him. As Juliet and Nick make their final goodbyes, Killabilly dies along with Nick.