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