Final answer:
Realism is the most impactful geopolitical theory on the global community, especially in geopolitics, due to its focus on state security and the balance of power among great powers.
Step-by-step explanation:
The most impactful geopolitical theory on the global community today, especially in geopolitics, is realism. Realism places states at the center of the system and focuses on maintaining the security of their state.
The theory emphasizes the balance of power among great powers and their spheres of influence in order to maintain world order. Realism has a significant impact on global security as it influences the actions and decision-making of states.