Achievements

Left 4 Dead includes achievements for Steamworks and Xbox LIVE. There are 73 achievements in all for the PC version of Left 4 Dead, but only 65 for the Xbox 360 version; the Outbreak achievement is not in the Xbox 360 version of the game and Survival Pack on Xbox 360 adds no new achievement due to technically being only a patch, not a DLC. There are currently 65 achievements for Left 4 Dead 2.

Survival Pack adds 7 new achievements to PC version of Left 4 Dead (no new achievement for Xbox 360 version of the game).

Downloadable Content Crash Course adds 10 new achievements to Left 4 Dead.

Downloadable Content The Passing adds 10 new achievements to Left 4 Dead 2.

Downloadable Content The Sacrifice adds 5 achievements to both Left 4 Dead and Left 4 Dead 2.

Note: Since the Crash Course update, achievements cannot be earned with cheats turned on (sv_cheats = 1). However, one way is to play on versus mode with everyone helping each other to get achievements.

Survival Mode
None of the Survival Achievements are present in the Xbox 360 version of the game since it is free DLC.

Miscellaneous
Achievements that don't fit anywhere else.