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 all three episodes
Complete episode 3
Give a gastroscopy
Locate the secret level
Pet two dogs
Early Access sauna is a cold place
Have a gastroscopy
I really like this random stuff
Kill 35 monster types
Kill or damage 10 monsters with landmines
Complete episode 2
Clean all mess after the Degustation
Kill 500 monsters in total
Kill all monsters in a level
Gib a horse
Start the mining train
Complete episode 1
Find a second pistol
Find all secrets in a level
Run over 10 monsters
Get past wave 10 in Endless Mode
Survive wave 5 in Endless Mode
Discover a secret of Vyšehrad Castle
Gottwald's body missing
Hit an enemy with the soccer ball
Achieve a score of 200 points on a handheld game
Kill 5 monsters with a sickle in a row without damage
Kill Headsman in air during jump
Get through a level without damage
A lot of wine
Anger the bees and run away
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
Waste three minutes watching the model railway
Free 4 Ratters
Shoot down a flying pigeon
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
Complete 6 different levels on Very High Difficulty
Check the simulator