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.
Slam Fritz Gessler's office door into him.
Kick Fritz Gessler's office door into him.
Knock Fritz Gessler out of his office window.
Intimidate Fritz Gessler into surrendering.
Free an innocent man at the expense of catching a guilty one.
Mock the chief of police at a critical moment.
Chicken out of telling Katie the truth at the last minute.
Tell Gessler that Rooke's hired you to betray him.
Complete a mission faster than I can.
Jump into an Enforcer to knock him through a window.
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 pounce instantly.
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.
Beat Fritz Gessler to death.
Knock Fritz Gessler out with a punch.
Shoot Fritz Gessler.
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.
Catch a guilty man at the expense of freeing an innocent one.
Upgrade your battery capacity to the non-figurative max.
Complete the police chief's missions without incriminating yourself.
Help justify my early, not entirely wise choice of game name by holding someone at gunpoint with the Resolver.
Conceal your presence at the DataSec break-in from Mayfield.
Voluntarily tell Katie the truth.
Steal Gessler's technology for Rooke.
Use no violence at all on a mission that has guards.
Complete a mission that has guards with no violence, witnesses or loud noises.
Upgrade your Bullfrog Hypertrousers to maximum jump strength.
Use the Hushcracker to jump through a window silently (outside of the test lab).
Use the Crosslink to create an infinite loop that burns itself out.
Get knocked down by an opening door.
Use the Dropshot to land silently from a great height.
Wire an elevator button to trigger something when the elevator arrives.
Knock a guard out by opening a door into him.
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.