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