Here is the full list of all 40 UnMetal achievements.
Finish the game without using a potty.
Finish the game on hard difficulty.
Complete "The Barracks".
Finish the game.
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.
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".
Obtain 5 potties.
Find 15 secrets in the game.
Get the maximum experience possible in at least 5 chapters.
Complete "Engineering Problems".
Reach level 8.
Defeat HUGEEL firing just 6 torpedoes.
Destroy 5 crates with the explosion of a single grenade.
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.
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.
Heal 20 guards.
Die while tampering with items from your inventory.
Destroy 5 drones by punching them.
Craft a Molotov cocktail.
Complete "Something Stinks Really Bad".
Reach level 4.
Defeat Sewerjunk without damaging it with the Flamethrower.
Kill 5 Human-Piranha-hybrid things with the shredders.
Neutralize 5 guards using the slingshot.
Complete "The Great Escape".
Reach level 2.