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