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