hold all the cards
hold (all) the cards
To be in a position of power or control over someone or something else. The phrase alludes to having the best cards in a card game (which would lead to victory). Now that Charlotte knows about us, she holds all the cards—I imagine it won't be long until she tells my wife what she saw. I saw my brother break the vase, so I hold the cards right now and can get him to do anything I want.