Here is the full list of all 37 Rebel Galaxy achievements. It takes around 50-60 hours to unlock all of the achievements on Windows.
Destroy 2,500 Fighter-Class Craft
Mine 50 asteroids using a Fault Tracker
Kill 20 Pirate Lords
Shoot down 500 torpedoes
Purchase a Dreadnaught-class ship
Destroy 1,000 Capital-Class Craft
Collect 100 bounties
Break 10 blockades
Successfully bribe a Militia official
Pirate a merchant
Complete the main campaign
Find the Face of Gozu
Find an Antimatter Speck
Reach a Net Worth of 50 Million Credits
Find a Progenitor Shard
Become neutral to pirate factions
Purchase a Destroyer-class ship
Break 1 blockade
Hack 10 transponders successfully
Reach a Net Worth of 5 Million Credits
Salvage 50 Containers
Gather 200 objects with a tractor beam
Kill 1 Pirate Lord
Complete 50 missions from the mission board
Reach rank 5 in any Guild
Rescue 20 merchants
Join the Mercenaries' Guild
Jump out of the first solar system
Become friendly to the Militia
Destroy 100 Capital-Class Craft
Collect 10 bounties
Destroy 250 Fighter-Class Craft
Join the Merchant's Guild
Woke Trell
Purchase a new ship
Trade with a Merchant while in flight
Hire a mercenary