Here is the full list of all 70 Heat Signature achievements.
Find an item that belonged to a Steam friend's character
Rescue a friend's character
Cause a guard to shoot themselves by Swapping with them
Complete an assassination mission without harming any other crew
Make it to a station after your pod has been destroyed
Complete a Ghost Clause
Cause a guard with a subverted shield to shoot themselves
Acquire a keycard while Visiting
Save someone with the Offworld Angel
Cause a sentry to shoot a guard by subverting it
Deliver an assassination target alive
Board a ship without docking your pod
Use a second Visitor before the first returns you
Teleport to an airlock with the Glitcher's Tick
Complete a Silence Clause
Complete a theft without being seen or harming anyone
Complete a Mistake mission
Reflect a bullet with an emergency shield
Complete your personal mission
Crash a shield
Take someone out with a melee attack less than 0.5 seconds after Sidewinding
Complete an Audacious (or harder) mission
Complete an Enigma Clause
Complete a Hard (or harder) mission
Complete a Bloodless Clause
Liberate a station
Catch a Rescue target in your pod while they're suffocating in space
Dock at a friendly station while on emergency fuel
Be rescued from your captor by the Visitor
Retire as a Living Legend
Find a unique item
Complete a practice mission
Retire Sader Fiasco
Complete a Pacifist Clause
Complete a Hijack mission in a Warzone
Complete an Assassinate mission without entering the ship
Knock a Capture target through a window
Start a new galaxy
Delete a Galaxy
Rescue one of your own characters
Knock yourself out with a wrench you threw
Break a ship with the Foundry Brick
Pass through a ship's vision undetected in the Sovereign Coldfire
Kill someone with a Shortblade within 1 second of killing someone with a Longblade
Completely eliminate a faction from the galaxy
Talk to Fiasco after liberating every Stronghold