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