What counterparty risk actually asks
Counterparty risk is often described as the risk that someone fails to pay. In an investment context the more useful formulation is broader: which entities have to remain solvent and operational for a position to be worth what a statement says it is worth?
Framed that way, the answer is rarely a single name. It usually includes the venue where a position is held, any broker or intermediary in the chain, the custodian holding collateral, an issuer whose instrument is being used as cash, and sometimes a lender on the other side of a financing trade. Each is a dependency, and each can fail independently of the market moving at all.