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