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