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 over 1987 Red Dudes in endless mode.
Unlock all endless levels.
Kill 3 Red Dudes with one shotgun shot.
Kill 100 Red Dudes with a rifle.
Launch every app in the system.
Find all secrets.
Kill an enemy by jumping on him.
Kill 3 Red Dudes with one rifle burst.
Kill 100 Red Dudes with a shotgun.
Become part of the community.
Kill 100 Red Dudes with a katana.
Cut bullet with a katana.
Kill 2 Red Dudes with one katana throw.
Upload a replay on killstagram.com
Complete the game.
Kill 100 Red Dudes using melee.
Score 100 headshots.
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.
Beat all Challenges.
Get RED ending in every level of SPEEDRUN challenge.
Get RED ending in every level of SPEEDRUNrt challenge.