The Hazari were a race of bounty hunters from the Delta Quadrant, who prided themselves on keeping their contracts more than the actual bounty itself. They were known as Species 4228 to the Borg, for whom they made excellent tactical drones. Certain members could resist a mind meld.
In 2375, Kurros of the "Think Tank" disguised as a Malon contracted the Hazari to capture the USS Voyager, as part of a plan to compel Seven of Nine to join their group. After discovering the deception, the Voyager crew captured two of the Hazari hunting them and made a new arrangement. The Hazari contacted the "Think Tank", first demanding triple the bounty and then threatening to destroy Voyager unless they were paid immediately. When the Think Tank probed Seven of Nine's mind to determine whether it was a trap, the Voyager crew was able to disrupt their communications and force their vessel to emerge from subspace. The Think Tank was then set upon by a dozen Hazari vessels. (VOY: "Think Tank")
According to the Star Trek: Star Charts (p. 91), there was a star system named Hazari, which might possibly be the system of origin for this species, in the Delta Quadrant. The system's primary was a K-class stars.