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