Here is the full list of all 20 Shadow Warrior Classic Redux achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Find 70 secret areas
Finish "Twin Dragon" expansion
Win 10 Pachinko games
Finish "Wanton Destruction" expansion
Slice 100 evil ninjas with Katana
Finish any level faster than 3D Realms time
Meet Sailor Moon
Watch TV in Seppuku Station
Finish "Code Of Honor" episode
Collect 50 fortune cookies
Hit 20 enemies with a vehicle
Defeat Sumo Demon boss
Kill 500 enemies
Defeat Serpent God boss
Finish "Enter The Wang" episode
Find Monty Python and The Holy Grail reference
Breed the rabbits to exhaustion
Fire Nuclear Missile
Kill 50 enemies
Use the Speed Racer RC car