Here is the full list of all 42 HALF DEAD 2 achievements.
Win twenty five times in cooperative mode
Win ten times in cooperative mode
In deathly room die from sculls
Fahrenheit 451
In deathly room die from chain
In deathly room die from teddy
In deathly room die from buckshot
Use torch to modify weapon twenty five times
Use nails to modify weapon twenty five times
Use poison to modify weapon twenty five times
Use electroshock to modify weapon twenty five times
Install wooden plank fifty times
Break lighter fluid fifty times
Use impulse grenade fifty times
Use bandage hundred times
Throw neurotoxin fifty times
Use flashbang grenade fifty times
Explode dynamite fifty times
Use first aid kit twenty times
Use pills fifty times
Win ten times in PVP mode
Discover seven hundred ten rooms
Win five times in PVP mode
In deathly room die by suffocation
Win once in PVP mode
In deathly room die from lasers
Find five hundred traps
In deathly room die from shark
Win five times in cooperative mode
Die from crocodile
Discover two hundred rooms
Find two hundred fifty traps
Discover hundred rooms
Find hundred traps
Win once in cooperative mode
Discover fifty rooms
Find fifty traps
Find twenty traps
In deathly room die from turbine
Find ten traps
Discover five room
Find five traps