Here is the full list of all 12 I Am Alive achievements worth 200 gamerscore. It takes around 8-10 hours to unlock all of the achievements on Xbox 360.
Help or rescue your first victim
Perform your first Quick machete kill while being bullied
Perform 3 Machete quick kills while being bullied
Repair the elevator to rescue the people stuck in the Fireworks episode
Perform 5 Machete quick kills while being bullied
Provide tomatoes to the hungry lady in the foggy streets
Help or rescue 3 victims
Help or rescue 5 victims
Help or rescue 10 victims
Finish the game once(any difficulty mode)
Finish game in Survivor mode
Rescue / help all victims in the game