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