Here is the full list of all 26 SUPERHOT achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Score 100 headshots.
Kill 100 Red Dudes with a katana.
Kill 100 Red Dudes using melee.
Kill 2 Red Dudes with one katana throw.
Cut bullet with a katana.
Upload a replay on killstagram.com
Complete the game.
Kill an enemy by jumping on him.
Get back to the system after being expelled.
Kill 100 Red Dudes with a pistol.
Complete SERV level.
Shoot down a bullet with a bullet.
Complete SUBWAY level.
Kill 100 Red Dudes with a shotgun.
Kill 100 Red Dudes with a rifle.
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.
Become part of the community.
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.