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