Here is the full list of all 22 Hellmut: The Badass from Hell achievements.
Complete Challenge mode in under 1 minute.
Deal over 100,000 cumulative damage.
Shoot 10,000 shots.
Die for the first time.
Complete Tutorial.
Enter dungeons as the Rat King.
Unlock all Transformations.
Buy one of each item type in shop.
Kill one of every enemy type.
Stay in the shop for more than 20 minutes continuously.
Don't lose a single hitpoint in one level.
Shoot 1,000 enemies with a single weapon.
Complete one playthrough in under 20 minutes.
Defeat The Demon.
Acquire Professor Transformation.
Enter dungeons as the Orc Fairy.
Collect 5,000 Soulstones cumulative.
Kill at least three enemies with an exploding barrel.
Use every weapon.
Kill The Demon at least 10 times after receiving Professor Transformation.
Play with all Transformations except the Professor.
Do 15.000 damage with barrels.