Assassin is a specialization of the Bounty Hunter career.
Whereas most Bounty Hunters focus primarily on the capture of quarry, those who specialize as Assassins are generally tasked with the straightforward proposition of terminating their targets. The selection of additional skills for an Assassin very much points towards this focus. Melee, Ranged (Heavy), Skulduggery, and Stealth.
Assassins can be found in the Edge of the Empire Core Rulebook.