the.com/kingfish

means The most powerful or important person in a group or operation — the one actually calling the shots, whatever their official rank says.

from Literally a name for large, dominant fish species (like the king mackerel) that rule their stretch of water — so 'kingfish' got hauled onto land in American slang as a label for human top dogs. It got a huge cultural boost from Huey Long, the Louisiana politician who embraced 'Kingfish' as his own nickname in the 1930s, turning a fish name into shorthand for the boss of a political machine.