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