diamond cut diamond
A situation in which two equally cunning or devious people spar or interact. Primarily heard in UK. It's always diamond cut diamond when those two schemers get together.
diamond cut diamond
a situation in which a sharp-witted or cunning person meets their match. British 1863 Charles Reade Hard Cash He felt…sure his employer would outwit him if he could; and resolved it should be diamond cut diamond.