Here is the full list of all 40 UnMetal achievements.
Finish the game.
Finish the game without using a potty.
Finish the game on hard difficulty.
Destroy General X's robo-tank without using electromagnetic grenades.
Break all toilet doors.
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.
Reach level 10.
Obtain Robert's photographs.
Destroy 9 mechanical spiders.
Heal 20 guards.
Neutralize 5 guards using the slingshot.
Complete "A Thousand Eyes Are Watching You".
Get the maximum experience possible in at least 5 chapters.
Complete "Boom Docks".
Put 20 guards to sleep.
Reach level 8.
Find 15 secrets in the game.
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".
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.
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".
Defeat Sewerjunk without damaging it with the Flamethrower.
Craft a Molotov cocktail.
Kill 5 Human-Piranha-hybrid things with the shredders.
Complete "The Great Escape".
Reach level 2.