The MOST important factor to consider when implementing cloud-related controls is the:

The most important factor to consider when implementing cloud-related controls is the shared responsibility model. The shared responsibility model is a framework that defines the roles and responsibilities of cloud service providers (CSPs) and cloud customers (CCs) in ensuring the security and compliance of cloud computing environments. The shared responsibility model helps to clarify which security tasks are handled by the CSP and which tasks are handled by the CC, depending on the type of cloud service model (IaaS, PaaS, SaaS) and the specific contractual agreements. The shared responsibility model also helps to avoid gaps or overlaps in security controls, and to allocate resources and accountability accordingly12.

References:

Shared responsibility in the cloud - Microsoft Azure

Understanding the Shared Responsibilities Model in Cloud Services - ISACA