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 using melee.
Get back to the system after being expelled.
Upload a replay on killstagram.com
Complete SERV level.
Complete SUBWAY level.
Shoot down a bullet with a bullet.
Kill 100 Red Dudes with a katana.
Kill 2 Red Dudes with one katana throw.
Kill 100 Red Dudes with a pistol.
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.
Cut bullet with a katana.
Kill 3 Red Dudes with one rifle burst.
Kill an enemy by jumping on him.
Unlock all endless levels.
Complete the game.
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.