Here is the full list of all 42 Gunpoint achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Voluntarily tell Katie the truth.
Knock Fritz Gessler out of his office window.
Use the Longshot to make a guard unintentionally shoot another (outside of the test lab).
Use the Prankspasm to knock out someone who isn't standing near a power socket (outside of the test lab).
Upgrade your battery capacity to the non-figurative max.
Upgrade your Bullfrog Hypertrousers to pounce instantly.
Shoot Fritz Gessler.
Catch a guilty man at the expense of freeing an innocent one.
Tell Gessler that Rooke's hired you to betray him.
Jump into an Enforcer to knock him through a window.
Use the Gatecrashers to kick a door through a window.
Use the Hushcracker to jump through a window silently (outside of the test lab).
Complete a mission that has guards with no violence, witnesses or loud noises.
Use the Gatecrashers to kick a door into a guard.
Use the Gatecrashers to kick a door off its hinges.
Publish your personalised epilogue.
Complete the game.
Beat Fritz Gessler to death.
Knock Fritz Gessler out with a punch.
Intimidate Fritz Gessler into surrendering.
Help justify my early, not entirely wise choice of game name by holding someone at gunpoint with the Resolver.
Knock a guard out by opening a door into him.
Use the Crosslink to create an infinite loop that burns itself out.
Upgrade your Bullfrog Hypertrousers to maximum jump strength.
Steal Gessler's technology for Rooke.
Use no violence at all on a mission that has guards.
Conceal your presence at the DataSec break-in from Mayfield.
Use the Dropshot to land silently from a great height.
Get knocked down by an opening door.
Wire an elevator button to trigger something when the elevator arrives.
Leave no living witnesses to your presence on a mission that has guards.
This is an achievement in name only. No-one admires you for punching a guy that many times.
Create a custom mission with at least one objective.
Complete a mission faster than I can.
Chicken out of telling Katie the truth at the last minute.
Complete the police chief's missions without incriminating yourself.
Mock the chief of police at a critical moment.
Free an innocent man at the expense of catching a guilty one.
Defeat Gessler by rewiring his gun.
Kick Fritz Gessler's office door into him.
Notice the story doesn't necessarily gel with the mechanics. Become qualified games journalist.
Slam Fritz Gessler's office door into him.