Bounty hunters: who are they?

Going by the most basic definition of the names, bounty hunters are men and women who hunt down and either arrest or kill a criminal or outlaw for whom a reward is offered for either their capture or death; basically the clawed arm of the law, where sometimes the arrested arrives in chunks... even while still alive. However, its more than that. WAY more than that, in fact.

Bounty hunters are essentially the real life equivalents of the adventurers of games and literature, taking the jobs that no one else can do (or wants to do for that matter), fighting criminals and monsters either alone or in small groups, with the permission of the Confederation, taking jobs from many sources: civilian corporations, peacekeeping forces, wealthy people, desperate people, shady organizations, and sometimes even the military and the Confederal Senate. Most of these come from military or peacekeeping backgrounds, but some are simply civilians that want to see the galaxy and have adventures without either joining the military or turning to mercenary work. As a sidefact, bounty hunters and mercenaries do not get along, especially since the former thinks of the latter as amoral killer for hire and the latter believes that the former steal money that was rightfully theirs.

Types

As said before, the idea of bounty hunting in which a single man or woman tracks down a criminal is simply one of the many types of bounty hunter that exists.
-'Normal' bounty hunters: these are the most common and known. Most of their jobs consist in simple search and arrest/execution (and when it's the latter, taking a tissue sample of the dead quarry), although it varies, from a single criminal to an entire group, and from simple murderers to entire criminal groups. One of the most famous (and living) is Herzlichen Masran, aimtroog and former heavy trooper, who managed to bring down the Red Dwarf mercenary group.
-Xeno-hunters: despite what the name may imply, these hunters do not exactly go after aliens (as in, other species other than their own); they hunt beasts, animals that cause trouble in a world and that most of the time can't be dealt with by the local peacekeeping force (and sometimes even the garrison). Many of them are simply invasive wildlife, which are animals that made their way to a world somehow (released pets that grew too much for their owners, escaped zoo animals and such) where they have no natural predators sans sophonts. A few of them, however, are native creatures that were thought to be extinct only to suddenly reappear in modern times and that are inherently dangerous, or even forgotten xenomorphs and titanic beasts from the Hegemony War that have survived until modern times. Many of these hunters track the aforementioned beasts right to their lairs alone, but some always have a loyal beast at their side, helping them tracking the monsters down and even aiding in its killing. The most famous xeno-hunter is Praeratus Haeleb, therawyrm and last living Centurion (although only government officials, the military and a few others know this last fact), and his gorgonops Cyranus.
-Head-hunters: these are nearly identical to bounty hunters, with two differences: they always kill their quarry, and rather than simply taking a tissue sample from it, they bring the entire head to make clear to the ones that hired them they did their job. There are no head-hunters of renown.
-Hunter-warriors: another variety of bounty hunters, these ones go mainly after war criminals, cult members of various cults and terrorists, and annihilate them in the most explosive way, usually by bombing their bases with kinetic ship armaments or going in guns blazing. The most known of the hunter-warriors is 'Tally', an älf cyborg that is also a sports star (specifically Jugger; Tally is not her real name) when not hunting.
-Delvers: these men and women brave derelict ships, ruined buildings, gigantic cave systems and other closed spaces to explore them or retrieve valuable objects. The most famous delver still alive is Moosk, a native of planet Reash who despite his 'quirks' is known for never backing down from a job, no matter where it brings him or how long it is.
-Psionic hunters: unlike most bounty hunters, most psionic hunters are, as the names says, psionics, and hunt down criminals of various kinds who can use them too and are too much for normal peace keeping forces to deal with. Most psionic hunters are from naturally psionic species, life älfs. The most famous psionic hunter, Coran the Magnificent, is in fact an älf.

There are more variants of bounty hunters out there in the Milky Way, but listing them all would be impossible.

Not a true chapter, but interludes do help to know the backstory of the 'Stellaris' side. This one, of course, is about bounty hunters, and many of the named ones are references to videogames and films.