Betrayal: You were personally betrayed by someone very close and dear to you causing your great heartache. (Work with your DM to detirmine the details)
Martial training: In adolescence you trained with the weapons of your people and learnt how to use them proficiently (work with your DM to determine details)
You become involved with criminal elements of society, taking to a life of crime and earning a notorious reputation and bounty. (work with your DM to determine details)