Here is the full list of all 26 SUPERHOT achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Kill 100 Red Dudes with a katana.
Kill 2 Red Dudes with one katana throw.
Cut bullet with a katana.
Become part of the community.
Complete the game.
Kill 100 Red Dudes with a rifle.
Get back to the system after being expelled.
Kill 100 Red Dudes using melee.
Kill 100 Red Dudes with a shotgun.
Kill 100 Red Dudes with a pistol.
Score 100 headshots.
Complete SERV level.
Upload a replay on killstagram.com
Shoot down a bullet with a bullet.
Kill an enemy by jumping on him.
Complete SUBWAY level.
Kill over 1987 Red Dudes in endless mode.
Kill 3 Red Dudes with one shotgun shot.
Kill 3 Red Dudes with one rifle burst.
Unlock all endless levels.
Find all secrets.
Launch every app in the system.
Beat all Challenges.
Get RED ending in every level of SPEEDRUN challenge.
Get RED ending in every level of SPEEDRUNrt challenge.