Another word for "top-level" is "highest-level" or "uppermost-level." These terms convey the idea of being at the very top or most important tier within a hierarchy or system. Depending on the context, other synonyms might include:

• Supreme: Often used to describe the highest authority or rank, such as a supreme court or supreme leader.
• Pinnacle: Refers to the highest point or peak of something, often used metaphorically.
• Apex: Similar to pinnacle, it denotes the very top or highest point.
• Summit: Often used in the context of meetings or conferences involving the highest-ranking officials, but can also refer to the peak of a mountain or achievement.
• Foremost: Indicates being at the very front or leading position in terms of importance or rank.
• Paramount: Suggests something of the greatest importance or highest priority.
• Chief: Often used to describe the highest-ranking person in an organization, such as a chief executive officer (CEO).
• Principal: Refers to the most important or primary level within a system or organization.
• Elite: Implies being part of the highest or most select group within a hierarchy.
• Premier: Often used to describe the highest-ranking or most important position, such as a premier league or premier minister.

Each of these terms carries slightly different connotations, so the choice of word depends on the specific context in which "top-level" is being used. For example, in a corporate setting, "executive-level" or "C-suite" might also be appropriate synonyms. In a technical context, "root-level" or "master-level" could be used to describe the highest tier of a system or process.