What term describes the person who is the decision maker and who is held accountable for successful completion of a task?

The term that best describes the person who is the decision maker and who is held accountable for the successful completion of a task is "Accountable." This term specifically denotes ownership and responsibility in a given context, especially in project management and organizational structures. An accountable individual not only makes crucial decisions but also bears the responsibility for the outcomes of those decisions, ensuring tasks are completed to the desired standard.

In organizational frameworks, such as the RACI model, the accountable person is often the one who has the final say and must answer for the results. This role is critical in ensuring that there is clear authority and responsibility, which aids in effective decision-making and successful project execution. Having someone who is accountable helps to clarify roles within a team, thus enabling better collaboration and accountability for results.