Here is the full list of all 13 Divided Skies achievements.
Steal a bike
Escape the sewers
Help out R.O.B. and Mittens
Stop the gang from attacking you
Escape the slums
Complete a time trial
Get a Bronze medal in a time trial
Get a Silver medal in a time trial
Get a Gold Medal in a time trial
Using hoverbikes to go upstairs is cool
Take down 30 Civillians
Be part of a tragic accident
Find all the collectibles spread throughout the slums