The default Agent Uninstall Password in Harmony Endpoint is a security feature that prevents unauthorized removal of the endpoint agent. Based on common practices in security software, the default password is often a simple, lowercase string that administrators are prompted to change after installation. In this case, the default password is 'secret'. This is a widely recognized default value in many systems, intended to be straightforward yet requiring replacement for enhanced security.

Option A, 'Secret', is incorrect due to its capitalization, as defaults are typically case-sensitive and lowercase. Option B, 'Chkp1234', could be plausible but is not a standard default for Check Point products in this context. Option D, 'RemoveMe', is intuitive but not a commonly used default. Therefore, the correct answer is C. secret.