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.
Finish the game once(any difficulty mode)
Finish game in Survivor mode
Rescue / help all victims in the game
Provide tomatoes to the hungry lady in the foggy streets
Repair the elevator to rescue the people stuck in the Fireworks episode
Ten victims helped
Perform 5 Machete quick kills while being bullied
Help or rescue 5 victims
Help or rescue 3 victims
Perform 3 Machete quick kills while being bullied
Help or rescue your first victim
Perform your first Quick machete kill while being bullied