Who was the Nadir shah

It was in the year 1739, Nadir Shar, the Shah of Iran and the founder of the Afsharid dynasty, invaded India. Before Nadir's invasion, India was not united as the states were fighting among each other. Nadir Shah took advantage of a weak Mughal Empire as the right opportunity to seize power and invade India. Nadir Shah advanced towards India in 1738. He captured the western frontiers of Mughal Empire such as Kabul, Ghazni, Lahore in 1739. The Mughal emperor, Muhammad Shah was defeated in the final battle and Delhi was captured by Nadir Shah and his forces. 
However, as soon as Nadir Shah ascended the throne of Delhi, riots sparked off in the streets of Delhi in which a number of Persian soldiers were killed. THis enraged Nadir Shah and he ordered a general massacre of Delhi, which was also known as the infamous “Qatal-e-am”. During this massacre, the citizens of Delhi were looted and raided. Many locations of Delhi like Dariba Kalan, Fatehpuri, Chandni Chowk, Hauz Kazi, Faiz Bazar, Lahori, Johri Bazar, Ajmeri and Kabuli gates, were soon covered with corpses of both Hindus and Muslims.