One Piece Roleplay: Laugh Tale
Now, while this server maybe new, it is steadily becoming a favourite due to having one of the craziest over-arching stories I've ever seen, and having some op as fuck chars. There's also the fact that it's a whole different beast than canon, to the point that the Pirate King's are different (Laugh Tale's Pirate King was called Dorado D. Ark, as opposed to canon's Gol D. Roger, which is made even more confusing as one of the main protaganist-type chararcter is called Gol D. Angelo)
Lets have a look at their Yonkous
First we got Shuten Douji, Captain of the Malignity Pirates (a Malignity is a group of goblins),basically Kaido if he had a Paramecia (the Blood-Blood fruit), he's currently in Impel Down after getting his ass handed to him by a Mexican Birkan Admiral. Is also a deadbeat dad like Kaido, except he's got two sons who are dead, one son who went and joined the Marines then became a Holy Knight, and a daughter trying to keep the Malignity Pirates together.
Next up we got Mary Indigo, Captain of the Eight Serpent Pirates, a bastard, if more successful, branch of the Kuja Pirates. She has the Repeat-Repeat fruit, an insanely busted Paramecia. Also the survivor of a domestic abuse incident involving the current Fleet Admiral, which has resulted in her and her crew hating both Men and the World Government to an unnerving degree.
Barto D. Porto, Captain of the Porto Pirates, and an absolutely unhinged motherfucker, combine Jabber from Gachiakuta with Teach and you've got this guy. User of the Distort-Distort Fruit, and has the biggest and most disfunctional pirate crew in the server, which is only kept together by his sheer charisma.
He also kidnapped a former admiral (she was already wounded from cutting her own arm off to save her son from a Celestial Dragon), who happened to be the daughter of the Fleet Admiral at the time. This would then kick off a series of events that would culminate in Alabasta going into isolation, a mass Impel Down breakout and the Enies Lobby War, which was basically Marineford kicked up to 11, as the full force of the Marines went against a pirate alliance consisting of Two Yonko, the Ryugyu kingdom, New World Pirates, and a bunch of Super-rookies.
Dorado D. Noah, basically combine Ace and Shanks and you get this guy. Son of the deceased Pirate King, and one of three Joyboy candidates (Barto is a self-proclaimed candidate, so he doesn't count), the other two being Gol D. Angelo who has the Straw Hat (literally Ace) and Marigol D. Buddy (Luffy, but if he was Mori Jin from God of High School) who has the Gomu Gomu no Mi (whether this is the Nika or not remains to be seen).
The newest Yonko, Romeo Figarland, he used to be the Supreme Commander of the God Knights, but has been labelled a Yonko after forming the Holy Figarland Empire and taking a massive chunk of the God Knights with him. The user of the Gravity Paramecia, and is basically a redhead Sephiroth (he is also a massive prick).