Players control Leon S. Kennedy, Chris Redfield, Jake Muller and Ada Wong as they confront the force behind a worldwide bio-terrorist attack.[13] The game also features a stamina bar; which depletes once the player performs melee attacks, or uses a "quickshot"—which involves shooting a zombie with a headshot instantly.In the PC version, the Mercenaries mode features an exclusive sub-mode named "No Mercy", which involves the cast from Left 4 Dead 2 fighting a total number of 300 enemies against a timer.He partners with Division of Security Operations (DSO) agent and Raccoon City survivor Sherry Birkin (Eden Riegel / Maaya Sakamoto) and learns that she is to extract him from the country to create a vaccine for the newly emerged C-virus.Meanwhile, a Bio-terrorism Security Assessment Alliance (BSAA) strike team, led by Chris Redfield (Roger Craig Smith / Hiroki Tōchi) and Piers Nivans (Christopher Emerson / Shuhei Sakaguchi), is deployed to eliminate the infected local populace.They are attacked by the leader of Neo-Umbrella, who claims to be Ada Wong (Courtenay Taylor / Junko Minagawa); she kills most of the team using a device that injects them with the C-virus, turning them into monsters, except Chris and Piers.On 29 June 2013, US President Adam Benford (Michael Donovan / Katsuhiko Sasaki) plans to publicly disclose the truth behind the 1998 Raccoon City incident and the government's dealings with Umbrella to prevent further bio-terrorism.The pair encounters the real Ada Wong (also Taylor), and Leon learns that National Security Advisor Derek Simmons (David Lodge / Takayuki Sugō) is affiliated with Neo-Umbrella and orchestrated the attack.On the oil platform, Chris and Piers head underground, freeing Jake and Sherry from captivity before preventing a large-scale attack by a massive bioweapon named Haos.They defeat Haos but, aware of his inevitable mutation, Piers sacrifices himself by pushing Chris into an escape pod and using his abilities to destroy the base.Although presumed dead after being shot by one of Simmons' soldiers, Carla attempts a final attack against Ada, after having injected herself with a powerful dose of the C-virus, but is killed.In a February 2012 interview, Hirabayashi stated that he went to lengths to balance "all of the things people love" about the series, so the team focused to orientate gameplay around horror themes.[26] In March 2012, Capcom admitted that it believed the survival-horror market was too small for Resident Evil, and issued a statement that the development team would instead choose to orientate the gameplay around the action genre.[27] The development of the game was led by Hiroyuki Kobayashi, who was stated by Capcom to be aiming to "deliver the most impressive Resident Evil title ever both in terms of scope and production values".[33] The decision to bring back zombies into Resident Evil 6 was made by Kobayashi, who felt that they were a popular component for the franchise, as well as complying per fans' requests.[46] Predator mode is a series of quick fire rounds with up to six players who take turns as the fearsome Ustanak and have full access to its weapons.Various weapons, characters and monsters from Resident Evil 6 have also been added as optionally downloadable replacement skins on the PC version of Left 4 Dead 2.[69] Hollander Cooper of GamesRadar praised the improvements to the controls over its predecessor, stating that the game had an emphasis placed on fluidity and movement, although noted that the cover system "never seems to work right".[3] The Escapist also praised the improved AI companion that "does a decent job of backing you up and taking the fight to the enemy rather than just standing by", while, however, disliking the cover system, calling it "the most forgettable new feature of the game".[77] According to Capcom, sales weakened following the strong start, with the company admitting that the game would not meet their goals, and consequently lowered their financial projections for the fiscal year.[78] In February 2013, Capcom said in a statement that the game suffered from poor sales due to various development challenges and "inadequate organisational collaboration" across the company.[82] Resident Evil 6 became Capcom's seventh-best-selling game by December 2023, selling 8.9 million units on PlayStation 3 and Xbox 360 with its original release.