Here is the full list of all 25 GRIDD: Retroenhanced achievements.
Gain a x24 multiplier in Arcade Mode
Access the Mainframe
Collect 100 power-ups
Destroy 200 fragments
Defeat the Facehugger
Make 100 bullets bounce
Charge the shield to maximum
Hack your first Backdoor
Survive your first Boss Fight
Destroy the first defense
Complete the Arcade Mode
Complete the Arcade Mode without using any Backdoor
Charge the weapon to maximum in Endless Mode
Gain a x32 multiplier in Arcade Mode
Annihilate Mainframe defenses
Kill 100 enemies
Complete the first Mainframe Sector
Access the 10th Mainframe Sector
Hack a total of 262.144 Kb
Hack a total of 524.228 Kb
Hack a total of 1.048.576 Kb
Access the 5th Mainframe Sector
Gain a Backdoor in Endless Mode
Survive at least 5 minutes in Endless Mode
Survive at least 10 minutes in Endless Mode