The most important characteristic of a key risk indicator (KRI) to enable decision-making is illustrating changes in risk trends, as it provides a clear and timely indication of the direction and magnitude of the risk level and exposure, and enables the stakeholders to take proactive andappropriate actions to address the risk.
The other options are not the most important characteristics, as they are more related to the monitoring, measurement, or identification of the risk, respectively, rather than the illustration of the risk trends. References = CRISC Review Manual, 7th Edition, page 110.