Here is the full list of all 40 UnMetal achievements.
Obtain 5 potties.
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.
Heal 20 guards.
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.
Complete "A Thousand Eyes Are Watching You".
Complete "Boom Docks".
Find 15 secrets in the game.
Get the maximum experience possible in at least 5 chapters.
Complete "Engineering Problems".
Defeat HUGEEL firing just 6 torpedoes.
Reach level 8.
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.
Put 20 guards to sleep.
Complete "Welcome to the Jungle".
Reach level 6.
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.
Neutralize 5 guards using the slingshot.
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.