Which insignia represents the highest enlisted rank E-9 in the Marine Corps?

The insignia that represents the highest enlisted rank E-9 in the Marine Corps is characterized by three chevrons above four rockers, along with the symbol of a bursting bomb. This specific design is recognized as the insignia for a Sergeant Major of the Marine Corps, which is the pinnacle of the enlisted ranks.

The three chevrons signify the rank of Sergeant Major, while the four rockers indicate the highest level of seniority within the enlisted structure. The bursting bomb symbolizes the Marine Corps' focus on explosive ordnance and combat readiness, which is central to its mission. The combination of these elements serves to highlight not just the rank but also the responsibilities that come with it, including leadership, mentorship, and operational excellence within the Marine Corps.

Other insignias listed represent different ranks or positions within the Marine Corps, but only the one with the bursting bomb accurately indicates the E-9 rank of Sergeant Major or Sergeant Major of the Marine Corps.