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