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