Here is the full list of all 40 UnMetal achievements.
Break all toilet doors.
Finish the game.
Finish the game without using a potty.
Destroy General X's robo-tank without using electromagnetic grenades.
Finish the game on hard difficulty.
Obtain 5 potties.
Complete "Jerico's Heart".
Complete the catacombs without destroying any cell gates.
Defeat TAKUMA TAKAGASHI without letting him heal himself.
Reach level 10.
Heal 20 guards.
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.
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.
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.
Put 20 guards to sleep.
Reach level 6.
Complete "Welcome to the Jungle".
Neutralize 5 guards using the slingshot.
Complete "In the Lion's Den".
Reach the ground floor in less than a minute when rushing to save the doctor.
Destroy 5 drones by punching them.
Die while tampering with items from your inventory.
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.