Sith are at once easier and harder to analyze than Jedi. Easier, because Sith factions tend to work in the long run, and harder, because for every Sith writer, there's a new way to write a Sith. Trying to break them down into groups is difficult. Nonetheless, we can still, with great difficulty, fit them most of them in.
That's what she said.
For Sith, you have a few basic groups. Bear in mind that most Sith who have been around for any length of time tend to mix and match, and plenty of them don't fall into any definable archetype.
The Edgelord- One of the more common options for new Sith writers. People, and by people I mean teenagers who are new to writing or alleged grownups who never got out of their goth phase, the Edgelord is reviled by just about everyone who has to deal with them. Cringey dialogue, terrible music choices, and actions that are solely designed to be as shocking as possible make for the sort of character that just makes you want to pick the writer up by the collar and slap some sense into them. The Edgelord is the sort of person who thinks Saw is a better horror movie than The Exorcist. Every now and again you'll see one who has a hint of self awareness, in which case the Edgelord jumps straight into self parody. Done right, this variation is absolutely hilarious. Done wrong, it's like every other instance of the Edgelord: utterly annoying.
The Bastard- What every Edgelord wants to be. The Bastard doesn't have to tell you they're a bad guy. They don't have to wear all black and sit on thrones made of skulls, though they might if the mood hits. They're so effortlessly evil that even a blind deaf mute would know to get out of their way. It takes a great deal of skill as a writer to pull this sort of character off, and even the really good ones can falter from time to time. Either they take it too far and drive people away, or they just get predictable, because you know they'll do the worst thing possible in any given situation. Ironically, some of the most evil Bastards I've encountered were written by the nicest people imaginable.
The Psychopath- Much like the Bastard, the Psychopath is a common path for reformed Edgelords. You never really know what they're going to do, because, if we're being fair, they don't either. A lot of folks think this sort of character works best as Chaotic Evil, but I disagree. I think Chaotic Neutral is far more compelling. It's not that they're evil, per se, it's that they're genuinely sick in the head, and don't view morality in the same way as the rest of us. You never really know how they're going to jump when the manure hits the air circulator. Maybe they save the kitten from the tree, maybe they stampede exploding goats through an orphanage. This sort of character tends to have a clear progression: they start off as cheap knockoffs of The Joker, but over time mutate into something like Hannibal Lector. Or at least they do if the writers possess any sort of skill. There are plenty that never get past the cheap Joker knockoff.
The Palpatine- The Palpatine is an extremely difficult character to pull off. They have to be charming and charismatic, while still being utterly ruthless. They have to have ambition, but it must be tempered by restraint. Most importantly, they have to be able to play the long game, planning and thinking months and years in advance IC. Done right, the Palpatine is one of the single most effective characters around in terms of leadership. To other Sith characters, the temptation is often to dismiss them as "not a proper Sith," because they're so in control of themselves. But beware: restraint is not the same thing as mercy. A good Palpatine keeps a list, and when your name gets to the top, they will screw you over so hard and so fast your head will spin. Fortunately, truly effective examples of this archetype are rare. Most Palpatines lack the patience and discipline, never mind the strategic acumen, necessary to really pull off the character. They've an annoying tendency to claim that everything is "all part of the plan," even when things go sideways. They're quick to take credit for victory, and quick to pass on the blame for defeat. Don't be that guy.
The Bane- Similar to the Palpatine in many respects, the Bane tends to play the long game. But whereas the Palpatine pursues power and authority for person the sake of personal ambition, a good example of the Bane will find themselves in positions of power as a natural consequence of who they are. They tend to focus on more personal stories over grand political intrigue, with character arcs involving a handful of characters spanning months and years OOC. Since their personal goals are more story oriented, they don't have to be as restrained or disciplined as the Palpatine; in fact, many of them can be quite brutal and stay true to their character and the archetype. Good examples of the Bane will find themselves with a close knit crew of writers. Bad examples of the Bane will try to form a close knit crew of writers, but no one can stand them. Expect to see apprentices come and go on a regular basis.
The Fallen- One of the more common starting points for Sith writers. Basically, a Jedi or similar Light Side user who fell to the Dark. This is one of those characters that's easy for even new and inexperienced writers to do well, because it comes with a built in set of motivations and emotions, along with several canon character examples to follow. They're often deeply conflicted about their choices, deeply guilt ridden, but determined to see their path through to the end. That's not to say that people who chose this route are being lazy; far from it. The Fallen is great for writers with established characters who want to try something new, or for new writers who are just getting into RP. Over time, they have a way of mutating into one of the other archetypes (it's not uncommon to see The Fallen dive straight into Edgelord territory before being dragged out by the scruff of their neck), but the best examples never forget their earliest motivations.
The Mad Scientist- One of the main advantages of being a Dark Sider is access to things like Sith Alchemy. The Mad Scientist pursues knowledge for the sake of knowledge, and typically only goes after power as a means to an end, that end being more knowledge or resources. The best mad scientists come up with stomach churning but incredibly useful tools and critters for their faction. New weapons, bio-engineering, Sithspawn, that sort of thing. Bad examples of the Mad Scientist come up with stuff like the Croa.
Sith factions tend to be much more successful than Jedi factions for one simple reason: they don't get hung up on the little things, so long as they have something to kill. They tend to accept that plotting and backstabbing are all part of the game. After all, one doesn't write a Sith without a healthy appreciation for ambition, and while they might not like being on the receiving end of someone else's betrayal, good Sith will be perfectly willing to put all that aside for a chance to return the favor.
Sith factions will typically form around a Bastard, a Palpatine, a Bane, or a coalition. All three archetypes influence the flavor and feel of the faction in different ways, and coalitions have their own distinct textures.
The Bastard is just so magnificently evil, other aspiring Bastards find themselves drawn to them like moths to a flame. Out of all the Sith factions, Bastard Sith factions tend to be the most short lived. Unless they have a Palpatine whispering in their ear, they have a nasty tendency to just wing it. Success breeds success, so when they start to gain momentum, they keep rolling over anything in their path. However, the wheels start to come off quickly if they can't keep that momentum up.
Palpatine Sith factions often start with a specific goal in mind, either IC or OOC. They tend to be more selective about who they let into their inner circles than the Bastard Sith, preferring to surround themselves with writers and characters who share their discipline and drive. A successful Palpatine faction is a thing of beauty and terror. They're often several steps ahead of both their opponents and allies, and the really good ones often find themselves accused of metagaming, because they're so good at getting into their heads of their opponents, they naturally assume that they have to be using OOC knowledge for IC gains. The bad ones actually are metagaming, so while the results might be superficially similar at first, in the long run they find themselves isolated and ostracized. The biggest threat to a Palpatine Sith faction isn't outside enemies, it's internal power struggles. In order to stay at the top, the leader has to maintain their dominance. At the slightest sign of weakness, their underlings are liable to start to plan and plot. A successful coup will go off with hardly a blip. A less successful coup is liable to shatter the faction in a million pieces.
Bane Sith factions are rare, because they're almost always the result of happy accident rather than intentional planning. Bane Sith tend to form small, tight knit groups. If the stories are compelling enough, other Sith writers will try to cluster around them to get in on the action. If all goes well for long enough, the group of writers grows and grows until it becomes a faction in its own right. Bane Sith factions might turn conquistador, but mostly they're focused on the story above all else. If they have a personal vendetta against another faction, they might move against them, grinding them into the ground and then burning what's left. However, this story driven approach isn't for everyone, so after a while, the groups start to shed members who are drawn to other, more ambitious factions. This usually doesn't bother the core writers much, since they'll keep on keeping on like they always have.
The most common sort of Sith faction is formed by OOC coalition. Rather than give power to an individual, these coalitions will usually have an NPC figurehead, while actual decisions are made by a committee of the most influential writers in the group. Unlike the other factions, they're usually motivated by an OOC goal, such as success in the map game, and they tailor their characters' stories to explain why they're all working together. So long as the core group of writers works well together, they can often expect a great deal of success in both the short and the long term, but once the core group gets bored and moves on to bigger and better things, the faction's days are numbered. Their replacements are often less well suited to leadership, and tend to serve shorter and shorter terms until things just fall apart.
Interacting with a Sith faction can be either a rewarding or frustrating experience. If you're a mercenary or soldier type, you can almost always find a home in their ranks, as they're usually good about making use of people who can fight. There's usually plenty of room for politicking, though many make it difficult for NFUs to gain IC power. They're also less prickly than Jedi when it comes to ideological purity, so if you have a Force user that generally aligns with their goals, if not their side of the Force, you can probably find a home. But, much like NFUs, the path to power is usually closed unless you convert to full on Sith.
For factions allied with a Sith faction, you can always count on a steady stream of ass kickers when it comes to invasions. There are more Sith who really know how to fight than Jedi, and more of them are willing to get into a brawl for fun. So long as you're not in their way, or you don't annoy them, Sith factions make for pretty good allies most of the time.
If you're facing them as an enemy, you basically have two options: bloody their nose early and hard, or expect to watch everything you love crumble. If you hurt them bad enough in the opening days of their campaign, they might move onto easier prey. If you don't, that'll just give their hype train extra momentum.
However, that doesn't necessarily mean that it has to be a frustrating experience. Just because they're stomping you into the ground IC doesn't mean they'll be assholes OOC. I mean, they can be. It happens. And if you start with the salt first, they're usually more than happy to return the favor, with interest. Because, you know, Sith. They write bad guys for a reason.
If you find yourself in their crosshairs and they're being assholes OOC without provocation, your best bet is to be polite and take notes. If they cross enough of the wrong lines, file a report. As tempting as it might be to respond in kind, you're probably not going to win that game.
So anyway, that's the gist of it. If you have any comments, or if you think I've missed something, lemme know in the comments.