chapter 84 - Akutagawa & Atsushi
volume 22 cover - Atsushi
Both Kenji and Mykola are compared to or portrayed as wildcards (in some games the joker acts as a wildcard).
Fyodor is shown both as a jack and as the one holding the card. He's a jack of spades, which is (most often) the highest suit. But he's in the hands of Sigma.
Atsushi and Akutagawa are obviously connected, as they're the new double black. It'd fit if they were a queen and a king, because in some games (for example 1000) they form a marriage, which is worth extra points and its suit becomes the strongest one. (Also the name "double black" could mean they are two black cards, and only cards of the same suit form a marriage).
Chuuya has to be a high card. His ability is powerful and Dazai says Fyodor used a "despicable" card
As for Sigma, I think they're outside of the card ranking. They're only holding the cards and Fyodor says they're more powerful than him and Dazai and a "foreign element to this world" - maybe because they're not a card, but rather the player? Or more: the ultimate player who'll get to make the final move. Dazai and Fyodor are the current players, but I believe Sigma will become one too. Chapter 106.5 suits this interpretation, as Dazai literally left the rest for them - maybe have them his cards?
What's more is that cards have four suits (club, spades, diamonds and hearts) and there are four main organisations / forces in the current arc: ADA, DOA, Hunting Dogs and PM (I'm not sure about PM, but idk what else and we got Aku and Chuuya present. And the Mafia played an important role at the beginning of ADA's chase).
If we take what I wrote about Fyodor being a spades, does it mean the DOA is the most powerful organisation? But even then, they're still held by Sigma, who's not really on their side (on their own or Dazai's). Also, even if they're the most powerful suit, the marriage (which I compared to Atsushi and Akutagawa), if formed, becomes the stronger suit.