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