Vallabhbhai Patel was bestowed the title "Sardar" for his leadership in the Bardoli Satyagraha. The Bardoli Satyagraha was a nonviolent movement that took place in Bardoli, Gujarat, India, in 1928. It was led by Vallabhbhai Patel and aimed at obtaining the reduction of land revenue taxes imposed by the British colonial government.

Option 2, Champaran Satyagraha, was a movement led by Mahatma Gandhi in 1917 in Champaran, Bihar, to address the issues faced by the indigo farmers.

Option 3, Khilafat Movement, was a political-religious movement by Indian Muslims in the 1920s to protest against the dismantling of the Ottoman Caliphate by the British.

Option 4, Quit India Movement, was a civil disobedience movement launched by Mahatma Gandhi in 1942 to demand an end to British colonial rule in India.

Thus, the correct answer is option 1, Bardoli Satyagraha, for which Vallabhbhai Patel was bestowed the title "Sardar" for his leadership.