Cressarch
A cressarch is a super who rules a state mostly by virtue of his superpowers, either having used them to conquer the state or their having been a major factor in his election to his position of leadership. A state ruled by a cressarch is called a cressarchy. Most cressarchs are supervillains, simply because it is supervillains, almost by definition, who desire power and dominion and who would be most likely to seek out a ruling position. Nevertheless, there may be benevolent cressarchs who truly try to do their best for their people—or autocratic cressarchs who consider themselves benevolent and rationalize that they seized power for the peoples' own good.
Cressarchs don't generally call themselves cressarchs; this is a term mostly used by carrologists and some political scientists. Like non-super rulers, cressarchs necessarily surround themselves with advisers, ministers, and other governmental officials. These functionaries may or may not themselves have superpowers, depending largely on the cressarchs' methods and the prevalence of supers in the world.
Elevation
Many cressarchs arrived at their positions simply by conquering an existing state. In some cases, the cressarch may have captured only a part of a state, using his powers to enforce its independence. In other cases, they may vanquish several bordering states, or parts of them, and unify them into a single domain. In any case, the neighbors and allies of the conquered states, not to mention whatever is left of their original governments, are likely to react to the new cressarch as they would any similar warlord, opposing his rule by both diplomatic and military means. However, a powerful super may be more than a match for whatever forces governments may throw against them. Even a less powerful cressarch may benefit from the aid of allies, not only friendly supers to whom they may grant positions in his government but other states who may have been enemies of those they conquered and see it as expedient to support the cressarch's new regime. Of course, as often happens in super worlds, perhaps the best counter for a super is another super, and superheroes often go up against upstart cressarchs to try to overthrow them and restore the status quo. In any case, though, a cressarch who manages to hold on for long enough becomes the new status quo, and may become an accepted part of the world's political landscape.
Not all cressarchs achieve their positions through conquest. There are those who rise through the normal political processes of their states, coming to their positions through popular election or through lawful appointment by their predecessors. This does not mean, of course, that their powers played no part in their achievement. It's quite likely that their superpowers made them a more attractive candidate or appointee, that they were given their position in large part because of their special abilities. It may even be that they used their gifts to directly influence the events that brought them to political power, such as by thelctically inducing voters to put them into office—though in this case it amounts to little more than a coup conducted by underhanded means. In any case, such subterfuges aside, such lawfully elected or appointed cressarchs are much more likely to be accepted as legitimate than those who gain their dominions by overt conquest, and will not necessarily face such strenuous opposition. Furthermore, cressarchs who attained power by lisible means are less likely to turn into the despots that those who rule by conquest often are—though it may, of course, happen that such a cressarch lets their power go to their head.
Succession
Like any rulers, cressarchs may be concerned about the continuation of their policies after their own deaths or retirements. The most tyrannical may not care for their people's wellbeing in the case that their state collapses into anarchy when they are gone, but their egos may mandate that they arrange for a like-minded successor to ensure that they are remembered positively.
If the cressarch's powers were an important factor in enforcing his leadership, then it stands to reason that to have a hope of holding that leadership a successor must have superpowers himself. Therefore, cressarchs are usually motivated to designate like-minded superpowered successors. Given the scarcity of supers on most worlds, this isn't always an easy task, and the cressarchs often find themselves forced to compromise, naming a successor who perhaps may not fully agree with all the cressarch's policies, but whose ways are at least close enough to not clash too much with the cressarch's desires. Of course, even if the succeeding cressarch is as powerful as the last, if they don't have the same powers—as they almost certainly will not—then there must still be some changes in the way they conduct their affairs, and there's likely to be considerable disruption. Rather than settle for a successor of less than perfect agreation to their policies, a cressarch may instead decide to name a successor whose ideals are more congenial to their own but who doesn't possess superpowers. This is especially likely if, as is often the case, the cressarch decides to name one of their children to the position, even though those children may not be supers themselves. The risk of the successor's not being able to hold their position may be mitigated by appointing superpowered guards and assistants to prop up their reign. This, however, introduces the new risk of those would-be assistants instead seizing power themselves.
Of course, many cressarchs don't bother to name a successor at all. This may be simply because they don't care what happens when they're gone (or because they're confident in their immortality and don't expect to ever be gone); it may be because they intend to but don't get around to it; or it may be a calculated decision under the (not unreasonable) concern that the appointed successor may decide to hurry along the succession. When a cressarch dies or retires without a named successor, it often leads to a free-for-all in which other local supers (and ambitious non-supers) vie for the metaphorical (and perhaps literal) throne. If no powerhungry supers in the area are up to the task—or capable of outmaneuvering the local superheroes who may be trying to stop them—then this may be the end of the cressarchy, with the state either splintering or dissolving into chaos, or reverting to non-super rule. On the other hand, if a new cressarch does seize power, and moves to decisively consolidate it, it may lead to the cressarchy becoming more oppressive then ever.
Demeanor
While some cressarchs downplay their superpowers, either to try to gain sympathy from false humility, to avoid attracting the attention of crusading heroes, or to foster the vainglorious impression that their powers weren't an important factor in their rise to rulership and that they could have achieved their position just as well without them, most cressarchs flaunt their powers instead, making sure that any subjects who might be inclined to rebel remember very well what they're up against. Some metarchs stage periodic ostentatious displays of their powers, perhaps on designated holidays or perhaps at random intervals. Others go so far as to theme the nomenclature of their government and society around their powers, giving government positions, administrative divisions, and so on names that somehow reflect their particular suite of abilities.
Supers are known to commonly have codenames, and cressarchs are no exception. On coming to power, however, a cressarch may rename themself the better to reflect their new position, swapping a less august name for one that they feel adequately advertises the grandeur of their position. Others, however, keep the codenames they had already established as supervillains (or heroes), perhaps valuing nostalgia over bombance. Still others on rising to power dispense with codenames altogether, feeling secure enough in their positions to not need to hide behind an onomastic mask. In some cases, such cressarchs even outlaw the use of codenames in their cressarchies—the better to impede the activities of heroes that might rise against them.
Relations
As with any ruler, the relationship of a cressarch with other heads of state depends largely on the cressarch's personality and attitudes, and the actions of their government. An expansionist cressarch who is constantly grasping at their neighbors' lands is unlikely to be popular. Nor is an isolationist cressarch who wants little to do with other nations in either trade or diplomacy, though they may at least not excite as much active opposition. But a cressarch willing to coöperate with other states when necessary may forge useful diplomatic relations and become a respected peer. While a cressarch who comes to his position by violently overthrowing an existing nation may certainly meet strong resistance at first, even such a ruler may eventually with shows of good faith, good conduct, and generous trade terms win over their fellow rulers and cause many of them (though not necessarily all) to forget their past offenses. It may even happen that other rulers look to the cressarchs, with their special powers, to help them with their own problems, in return for favors or concessions. Wily cressarchs may welcome such overtures as opportunities to strengthen their power over the other nations they deal with and make inroads to bringing them under their thralls.
On those rare worlds (such as Gallerra) that have many cressarchies, the cressarchs of the different nations may or may not get along. There are likely to be complex webs of alliances and rivalries among the various cressarchs, just as there commonly are with rulers elsewhere.