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