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