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