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