Here is the full list of all 28 Viscera Demo achievements.
Kill your first enemy boss
Survive 10 minutes on any level using only Rifle
Survive 15 minutes on any level using only Rifle
Survive 20 minutes on any level using only Rifl
Use Laser type weapon for 5 minutes on any level and don't get overheat
Kill 500 monsters on any level without dying
Kill 2000 monsters on any level without dying
Use Double-Barrel Shotgun on any level to kill 1000 monsters
Achieve Gold Medal at "Abandoned Factory"
Achieve Bronze Medal at "Highway"
Survive for 10 minutes at any level with Fire weapon
Deal 100'000 damage with explosive weapons without dying
Achieve Silver Medal at "Downtown"
Install "Exoskeleton" implant
Install "Hazmat Suit" implant
Install all implants
Install "Maximum Catalyst" and "Maximum Luck" implants
Use Laser type weapon for 10 minutes on any level and don't get overheat
Destroy 50 enemy devices like turrets or teleports without dying
Use any Bolt weapon on any level to kill 800 monsters
Use Slugger to destroy 15 enemy devices without dying
Use Minigun for 5 minutes on any level and don't get overheat
Deal 500'000 damage with Slugger type weapons without dying
Deal 50'000 damage with a "Gravity Rifle" without taking any damage
Kill 1000 monsters with any Gravity weapon without taking any damage and changing weapon
Achieve Platinum medal on any level
Deal 1'000'000 damage with a plasma weapon
Deal 10'000'000 damage with an explosive weapon