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