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Skull is the only one that even makes sense. The rest range from generic concepts with nothing else to them (Rocket is the mafia, that's about it) to having outright nonsensical end goals (HEY GUYS WHAT IF WE FLOOD THE WORLD LOL).
Skull is a bunch of rebellious teenagers run by a guy who resents the established island challenge because he failed at it. Aether as a whole isn't great but Lusamine is decent and the rest of the Foundation existing around her at least makes sense, as does how she got Guzma to work with her.