The idiom "hold all the aces" means to have a very strong advantage or control over a situation. It comes from the game of poker, where having a hand of aces is considered the strongest possible hand.
When you use this idiom, you are saying that someone has all the power or advantages in a particular situation. For example, if a company has a monopoly on a certain product, they could be said to "hold all the aces" in that market. Or, if someone is negotiating a deal and has all the information and leverage, they could be said to "have a hand of aces" in the negotiation.
Overall, this idiom is used to describe a situation where someone has a clear advantage over others, and it is often used in business or competitive contexts.