Here is the full list of all 12 Choplifter HD achievements.
Complete the game on NORMAL
Get 5 Stars on all levels
Complete all "Escape" missions without killing anyone
Kill 100 enemy soldiers on one level, without restarting the level
Complete a level by killing all the rescuees
Kill 10,000 enemies across all the levels
Complete Desert Rescue without letting any rescuees die
Save Scoop on every level he is present
Find all secrets
Kill 1,000 chickens
Kill 1,000 zombies
Make 100 goats faint