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