Achievements

Left 4 Dead includes achievements for Steamworks and Xbox LIVE. There are 51 achievements in all for the PC version (not including the 7 from Survival Mode, or the 10 from Crash Course), but only 50 for the Xbox 360 version (not including the 10 from Crash Course); the Outbreak achievement is not in the Xbox 360 version of the game.

Note that none of these achievements can be achieved with cheats turned on.

Cheats can be used to unlock achievements, all you have to do is kick all the players through the console then turn on  and , then fly to the end of the level then turn off noclip and. Repeat this through all the levels in a campaign and achievements can be easily unlocked through this. For example, if you want Man vs. Tank, kick all players then  in the air with   look directly at your feet and   then turn off. The Tank will not be able to attack you even with the rock throw and he just runs back and forwards under your feet.

Note that achievements cannot be reset, so if you decide to cheat then there is no way to get the achievement later without cheating.

Survival Mode
All of the Survival Achievements are not present on the Xbox 360 version of the game since it is free DLC.

Left 4 Dead 2
New achievements are detailed here.