Here is the full list of all 43 G-Force achievements worth 1,000 gamerscore. It takes around 15-20 hours to unlock all of the achievements on Xbox 360.
Complete the game on 'Normal' difficulty
Complete the game on 'Challenging' difficulty
Complete the game on 'Special Agent' difficulty
Complete the game in under 8 hours
Complete the game twice
Fully upgrade character with all possible weapons and upgrades
Achieve an average hit rate of 80% with projectile weapons
Complete the game on 'Easy' difficulty
Finish mission
Collect 100% (50) of all Silver Data Disks
Defeat 100 enemies with the Flame Thrower
Purchase all new weapons and weapon upgrades
Defeat 50 enemies using NanoHacked enemies
Defeat 50 enemies with Incendiary Charges
Travel more than 2km using Mooch
Defeat 100 enemies frozen by the Freeze Gun
Defeat 1000 enemies
Defeat 50 enemies with RDV Homing Missiles
Travel more than 20km using Darwin
Defeat 50 enemies with the RDV Pulse Cannon
Collect 50% (25) of all Silver Data Disks
Spend more than 10000 SaberSense chips at the kiosks
Defeat 100 enemies with the Shot Bolter
Scan 100 items in the game
Defeat 500 enemies
Defeat 100 enemies with the Cluster Rifle
Defeat 100 enemies with the Plasma Gun
Accumulate more than 5000 SaberSense chips
Defeat 100 enemies