Kazon sects control this part of the quadrant. Some have food, some have ore, some have water. They all trade and they all kill each other for it.
~ Neelix on the Kazon.
The Kazon are a brutish humanoid race of aliens from Star Trek Voyager that made their first appearance in the pilot episode "Caretaker". A warrior race, the Kazon were crude and violent with the dubious honor of being the only known species the Borg refuse to assimilate because they view them as unworthy.
Kazon are not very intelligent nor particularly dangerous but they have a pack mentality not unlike gangs or primitive tribal societies, as such they can be threatening and are known to attack other species as raiders and opportunists. A male-dominated society Kazon are very much the stereotypical brute race and male Kazon do not take kindly to females giving them orders: they have no objection to mistreating and even torturing prisoners (as they did to a young Kes).
Kazon are comparable to species such as the Klingon (of TNG and later, not the Soviet-inspired Klingons of TOS) or the Orion and were inspired by actual street gangs, hence their aggressive and primitive society. At some point in the past, the Kazon were enslaved by the Trabe. In 2346, the Kazon overthrew their Trabe masters, taking their ships and technology. The Trabe were forced to become a nomadic species following the Kazon revolt.
The Kazon fell into factionalism, with the various Kazon sects fighting each other for control of territory and resources. When the Federation starship Voyager appeared in the Delta Quadrant the Kazon sects began competing to acquire replicators, transporters, and other Federation technology in order to get a leg up on the other sects and establish themselves as a major power in the Delta Quadrant.
The Kazon-Nistrom were able to capture Voyager for a brief period at the end of 2372, but the ship was retaken thanks to the efforts of the Doctor, Lon Suder, Tom Paris and a group of Talaxian soldiers. Voyager soon moved beyond Kazon space, leaving the species behind in the Delta Quadrant.