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