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