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.
Beat all Challenges.
Get RED ending in every level of SPEEDRUN challenge.
Get RED ending in every level of SPEEDRUNrt challenge.
Kill 100 Red Dudes with a rifle.
Kill 100 Red Dudes with a katana.
Become part of the community.
Launch every app in the system.
Upload a replay on killstagram.com
Cut bullet with a katana.
Complete the game.
Find all secrets.
Kill 3 Red Dudes with one shotgun shot.
Get back to the system after being expelled.
Kill 2 Red Dudes with one katana throw.
Complete SERV level.
Kill 3 Red Dudes with one rifle burst.
Kill an enemy by jumping on him.
Score 100 headshots.
Kill 100 Red Dudes with a shotgun.
Kill 100 Red Dudes using melee.
Kill 100 Red Dudes with a pistol.
Complete SUBWAY level.
Shoot down a bullet with a bullet.