Which type of agent has the broadest authority to act on behalf of their principal?

The type of agent that has the broadest authority to act on behalf of their principal is a universal agent. A universal agent has the capacity to perform any act that the principal could perform personally, granting them extensive powers. This includes legal authority to make decisions and take actions that are not confined to a specific task or set of tasks; essentially, they can manage affairs in a comprehensive manner.

Universal agents are often used in situations where a principal needs someone who can handle a wide range of activities on their behalf, such as managing a business or handling all personal matters. This broad scope of authority distinguishes them from other agent types, which may have limitations defined by specific duties or contexts.

General agents possess authority to act on behalf of the principal in a particular business or area, but their powers are not as extensive as those of a universal agent. Special agents are appointed for a specific purpose or transaction and have limited authority. Sub-agents serve under a general agent and their authority is limited to what the general agent specifies. Thus, the universal agent stands out due to the expansive nature of their authority, allowing them to act in many areas related to the principal's interests.