FlatOut 2, the sequel to the original 2004 FlatOut, was published by Empire Interactive and released across Windows, PlayStation 2, and Xbox in mid-2006. The game placed emphasis on street and import tuner culture, refining the tire grip mechanics so players had greater control through corners compared to the first title. Its standout feature was ragdoll physics: drivers could be hurled from their cars in collisions or launched deliberately in a series of stunt minigames. These minigames challenged players to use the airborne driver like a projectile, targeting bowling pins, dartboards, field goal posts, and flaming hoops. Aerobatic controls allowed limited in-flight direction, while a "nudge" mechanic could extend a driver's trajectory at the cost of drag. Ultimate Carnage was released the following year as the definitive edition of FlatOut 2, known during development under the working title FlatOut: Total Carnage.
Ultimate Carnage introduced Carnage mode, a dedicated challenge series comprising 36 events spread across stunts, demolition derby deathmatches, carnage races, and timed bomb-evasion events. This mode gave the game a structured competitive identity beyond the standard race calendar.
The vehicle roster was presented with greater technical detail than any previous FlatOut title. Each car was constructed from up to 40 separate destructible components, and the physics and damage engines received substantial upgrades. Dynamic lighting and shadow rendering were updated to reflect the capabilities of the Xbox 360 hardware. Single-player events could field up to 11 AI-controlled opponents simultaneously, producing densely packed, destructive race scenarios.
Multiplayer was handled through the Games for Windows Live infrastructure on PC and Xbox Live on Xbox 360. Players were required to sign in with an Xbox Live or Games for Windows Live account, and the LAN functionality present in FlatOut and FlatOut 2 was not carried over to Ultimate Carnage.
FlatOut: Ultimate Carnage launched in Europe on 22 July 2007, followed by Australia on 1 August and North America on 2 October, exclusively for Xbox 360. The Windows version arrived later via Steam on 26 August 2008 and in retail stores on 2 September 2008. A handheld companion release, FlatOut: Head On, was developed for PlayStation Portable and released in March and April 2008 across Australia, Europe, and North America.
Critical response to the Xbox 360 and PC versions was favorable. Hyper's reviewer praised the title for "looking and playing better than ever before," though noted concerns about lengthy load times and a divisive soundtrack. Japanese outlet Famitsu awarded the Xbox 360 version 27 out of 40. Head On received more mixed assessments. Review aggregator Metacritic categorized the console and PC versions as receiving favorable reviews overall.
Ultimate Carnage represents the peak of Bugbear's FlatOut 2 engine before the studio moved to new projects. The ragdoll stunt system it popularized became a defining characteristic of the FlatOut brand, widely referenced as an example of physics-based comedy in racing games. The PC version received continued support into the modern era: a July 2024 update implemented Steam Workshop support, improved compatibility with Steam Deck, and added quality-of-life refinements, demonstrating sustained interest in the title more than 15 years after its original release. A PlayStation Portable companion title, FlatOut: Head On, extended the game to handheld audiences. An OS X port was published in 2008 by Virtual Programming.