Final answer:
Suleiman I, also known as the Magnificent, was the ruler of the Ottoman Empire who is regarded as the greatest sultan. His reign was marked by significant achievements and reforms, including the creation of a unified legal code for the empire.
Step-by-step explanation:
The ruler of the Ottoman Empire who is regarded as the greatest sultan was Suleiman I, also known as the Magnificent. He was known as 'the lawgiver' for his creation of a legal code that applied throughout the empire. Under his rule, the Ottomans reached their greatest heights and made important advances in fields such as astronomy and medicine. Suleiman's reforms and accomplishments won him wide acclaim and popularity among the Ottoman subjects.