Here is the full list of all 35 Droid Assault achievements.
Defeated Level 20 Boss
Achieved security level 2
Achieved security level 4
Achieved security level 3
Got Red Alert status
Achieved security level 5
Defeated Level 10 Boss
Achieved security level 1
Escaped with 0 hitpoints and no squad
Buffed a droid in every aspect
Defeated Level 30 Boss
Defeated Level 40 Boss
Completed Arcade Missions
Got Red Alert twice on one level
Achieved security level 6
Achieved security level 7
Achieved security level 8
Achieved security level 9
Captured the Ultimate Droid
Command a full squad of 8 droids
8 droids in ascending security order
Captured 3 9-series robots in same squad
Maximum Recharge buff
Maximum Battery buff
Maximum Overdrive buff
Maximum Armour buff
Maximum Damage buff
Maxed every buff on a droid
Flame, laser, and disruptor resistant droid
Everything-proof and maxed-buffs droid
Fried 100 robots
Crushed 25 robots in doors
Destroyed 100 robots with the disruptor
Defeated a boss with only a Sec Level 1 droid remaining
Started a level with 8 droids, finished with only 1