One Sith.
No, not the Mandalorian factions that I'm also pretty biased towards and at times even led myself. Nah, One Sith takes the cake by a mile for me.
I got involved later on when Invasion discussions got heated and filibustery, as a cooler head to try and lower the temperature.
But my favorite part was the very strong leadership from the start, far before I ever joined. Other Sith factions were developing and trying to get recognition, but One Sith made very strong and bold decisions that set them apart and began to suck the air out of their Sith competition. For perspective, I believe they were a Minor faction for some 4-5 months (maybe 6) before they finally erupted on the map in the biggest of ways.
1) Vengeance on the Republic for defeating the OG Sith Empire. Never waver. Keep your eye on the ball.
2) No Discord. No Skype. No chat. We’re here to roleplay. We’re here to immerse. Oh our members want a Discord? No. Roleplay or go sit on the sidelines and witness me. Only when leadership changed in the faction did they cave, well after the war. I remember asking them early on if they had one and the answer was a modest, simple "nah." It kinda wow'd me, tbh.
3) Coruscant. Don’t waver. We’re wrecking Coruscant, right at the heart of the Republic.
4) Roleplay to have a voice. If not, you have no say. Also, NPC Emperor. This isn’t about social heirarchy or clout chasing. Sith vengeance at it’s purest. That’s what we’re about.
That history of Chaos - from the very first Invasion of Mandalore, to the Republic finally breaking the Sith Empire, to the One Sith emerging as not only a powerhouse of revenge seemingly out of nowhere to wreck the capital of the Republic - but THE powerhouse on the map that everyone would soon have to deal with - that was premium Chaos for me. It's also one of the few times in the early days I wasn't behind the scenes trying to help a faction out, whether with advice or art or coaching "Tef's 101 How To Hype Train". We've seen more organic awesomeness from the community since, which I also enjoy, but this one particularly will sit with me as a "oh, I wouldn't have thought to run things like that." with a splash of "those guys must've been having an absolute blast."