Here is the full list of all 40 UnMetal achievements.
Let SPLASH MIKE destroy all crates and trucks at the barracks.
Finish the game on hard difficulty.
Defeat Sewerjunk without damaging it with the Flamethrower.
Heal 20 guards.
Kill 5 Human-Piranha-hybrid things with the shredders.
Obtain 5 potties.
Destroy 5 trucks in the barracks north parking lot before SPLASH MIKE does with his tank.
Craft a Molotov cocktail.
Die while tampering with items from your inventory.
Neutralize 5 guards using the slingshot.
Destroy 5 crates with the explosion of a single grenade.
Reach level 10.
Finish the game.
Finish the game without using a potty.
Destroy General X's robo-tank without using electromagnetic grenades.
Destroy 5 drones by punching them.
Break all toilet doors.
Complete "Jerico's Heart".
Complete the catacombs without destroying any cell gates.
Defeat TAKUMA TAKAGASHI without letting him heal himself.
Have 90 or more bullets at the same time.
Obtain Robert's photographs.
Destroy 9 mechanical spiders.
Find 15 secrets in the game.
Get the maximum experience possible in at least 5 chapters.
Complete "A Thousand Eyes Are Watching You".
Complete "Boom Docks".
Reach level 8.
Put 20 guards to sleep.
Complete "Engineering Problems".
Defeat HUGEEL firing just 6 torpedoes.
Complete "The Barracks".
Reach level 6.
Complete "Welcome to the Jungle".
Complete "In the Lion's Den".
Reach the ground floor in less than a minute when rushing to save the doctor.
Reach level 4.
Complete "Something Stinks Really Bad".
Complete "The Great Escape".
Reach level 2.