Here is the full list of all 47 Titan Attacks achievements.
Captured 25 live aliens
Killed 100 parachuting aliens
Everything maxed out
Completed the Titan levels
Guns and addons maxed
Upgraded addons to maximum rate
Perfect Challenge Level 77
Killed 50 parachuting aliens
10 aliens escape capture
Maxed gun bullets
Added all addons to ship
Perfect Challenge Level 42
Perfect Challenge Level 21
Completed the Saturn levels
Maxed gun power
Completed the Mars levels
Got 100 skill shots
Killed 25 parachuting aliens
Completed the Moon levels
Perfect Challenge Level 35
Killed 10 parachuting aliens
Destroyed 25 saucers
Got 50 skill shots
Completed the Earth Levels
Got 25 skill shots
Captured 10 live aliens
Destroyed 10 saucers
Got 10 skill shots
Got the x9 multiplier
Perfect Challenge Level 7
Perfect Challenge Level 14
Perfect Challenge Level 28
Perfect Challenge Level 49
Perfect Challenge Level 56
Perfect Challenge Level 63
Perfect Challenge Level 70
Perfect Challenge Level 84
Perfect Challenge Level 91
Perfect Challenge Level 98
Captured 50 live aliens
Captured 100 live aliens
25 aliens escape capture
50 aliens escape capture
Destroyed 50 saucers
Destroyed 100 saucers
100 aliens escape capture
Used 25 smartbombs