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