Here is the full list of all 55 HROT achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Complete 6 different levels on Very High Difficulty
Check the simulator
Complete all three episodes
Complete episode 3
Give a gastroscopy
Find a postcard from the creators of Project Warlock 2
Find Tuzex vouchers
Kill or damage 10 monsters with landmines
Kill a monster by knocking it off somewhere high with the footkick
Burn 4 monsters with one bottle
Hit the enemy with a kicked grenade
Have a gastroscopy
Surprise the newt in the cabin
I really like this random stuff
Early Access sauna is a cold place
Shoot down a flying pigeon
Free 4 Ratters
Locate the secret level
Pet two dogs
Waste three minutes watching the model railway
Find 50 different secrets
Find all plates in the Granny's Valley and bring them to the Degustation
Kill 35 monster types
Get past wave 15 in Endless Mode
Complete episode 2
Clean all mess after the Degustation
Anger the bees and run away
A lot of wine
Get through a level without damage
Kill Headsman in air during jump
Kill 500 monsters in total
Gib a horse
Kill all monsters in a level
Start the mining train
Kill 5 monsters with a sickle in a row without damage
Achieve a score of 200 points on a handheld game
Find all secrets in a level
Discover a secret of Vyšehrad Castle
Hit an enemy with the soccer ball
Get past wave 10 in Endless Mode
Survive wave 5 in Endless Mode
Complete episode 1
Gottwald's body missing
Find a second pistol
Run over 10 monsters