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