Here is the full list of all 10 Bounty Hunters achievements.
Become a Level 1 Character
Kill the slums boss on the roof.
Kill the nightclub boss in SIN
Survive all the waves in Downtown.
Survive all the waves in Housing.
Survive all the waves in Slums.
Survive all the waves in Subway.
Survive all the waves in Underground.
Survive all the waves in Uptown.
Kill a Bounty Hunter.