Final answer:
The Marathas, led by Shivaji, posed the most significant challenge to the Mughal Empire, effectively resisting and undermining Mughal rule in several regions.
Step-by-step explanation:
The group that posed the greatest challenge to the Mughal Empire was the Marathas. The Marathas, hailing from the western uplands of the Deccan Plateau, significantly undermined Mughal authority during the reign of Emperor Aurangzeb. Their most notable leader, Shivaji, consistently defeated Mughal commanders, ultimately affecting the Empire's stability.
The Maratha's military acumen was honed serving in the armies of various regional powers, enabling them to exploit Mughal weaknesses effectively. Shivaji's guerrilla tactics, combined with his command of a disciplined and mobile cavalry, allowed the Marathas to capture territories like Gujarat and maintain prolonged resistance against larger Mughal forces.
Despite the Mughal Empire's early successes with gunpowder weapons and their extensive territorial reach under rulers such as Babur and Akbar, internal uprisings, external pressures from other empires (e.g., British East India Company), and the inherent administrative challenges of governing a vast empire all contributed to their eventual decline. The Maratha's persistent opposition was a critical factor in this process, reflecting the growing regionalism that characterized the late Mughal era.