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