It has been proven impossible to reach full consensus at scale in a fully decentralized, asynchronous system (the FLP theorem).

So, in computer science terms, consensus algorithms are about approximating distributed consensus in the face of benign and malicious threats or communication failures, which devolves to "quorum / majority" pretty quickly in a crisis.

After the crisis, some kind of compensation, reconciliation or excommunication has to happen with the portion that disagreed.