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