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