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