Here is the full list of all 40 UnMetal achievements.
Finish the game on hard difficulty.
Reach level 10.
Heal 20 guards.
Find 15 secrets in the game.
Get the maximum experience possible in at least 5 chapters.
Defeat Sewerjunk without damaging it with the Flamethrower.
Finish the game.
Finish the game without using a potty.
Destroy General X's robo-tank without using electromagnetic grenades.
Break all toilet doors.
Neutralize 5 guards using the slingshot.
Complete the catacombs without destroying any cell gates.
Complete "Jerico's Heart".
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.
Complete "A Thousand Eyes Are Watching You".
Complete "Boom Docks".
Reach level 8.
Put 20 guards to sleep.
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".
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.
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.
Die while tampering with items from your inventory.
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.