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