Directions: Which ruler presided over the Sikh Empire during its period of peak territorial extent and ultimate apex?

The correct option is Maharaja Ranjit Singh.

Explanation:
Maharaja Ranjit Singh, popularly known as Sher-e-Punjab (the Lion of Punjab), was the founder and sovereign ruler of the Sikh Empire. He successfully united the disparate Sikh misls (confederacies) into a powerful, centralized empire at the turn of the 19th century.

Under his reign from 1801 to 1839, the empire expanded across the Punjab region, stretching from the Khyber Pass in the west to western Tibet in the east, and from Kashmir in the north to Mithankot in the south. This era represented the peak of the empire's military prowess, territorial expanse, and cultural prosperity.

Brief Context on Other Options:
- Banda Singh Bahadur: A celebrated Sikh warrior who led campaigns against the Mughal Empire in the early 18th century, well before the formal establishment of the Sikh Empire.
- Maharaja Duleep Singh: The youngest son of Ranjit Singh and the last Maharaja of the Sikh Empire, whose reign saw the Anglo-Sikh Wars and the eventual annexation of the empire by the British East India Company in 1849.
- Hari Singh Nalwa: The legendary Commander-in-Chief of the Sikh Khalsa Army who expanded the empire's frontiers, but served under Maharaja Ranjit Singh rather than presiding as ruler himself.