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