In the words of the @0xPolygon Founder, @sandeepnailwal, he defined the Pessimistic proof as a ZK security solution that makes sure no chain can withdraw more from the shared bridge than they deposited. Describing further, Pessimistic proof is simply a zk-security for cross-chains interoperability, also a cryptographic solution integrated into the Agglayer to treat all chains as unreliable and will strictly investigate them. In other words: The Pessimistic proof is a protective and defensive coverage over transactions in the Agglayer across diverse cross-chains, with smooth communication and interaction between those chains.