Here is the full list of all 21 Syndrome achievements.
Access deck 5
Survived a trap
Got the Valkenburg running again
Deactivate the ship's firewall
Defeat the Beast
Complete the game
Read all logs
Cure 500 Hp of damage
Have a droid working for you
Pick up tool
Pick up pistol
Pick up SMG
Pick up Cannon
Pick up hacking device
Access deck 1
Access deck 2
Access deck 3
Access deck 4
Access deck 6
Access deck 7
Access deck 8