Wikipedia
Vishwas Rao (March 7, 1741 – January 14, 1761) was the eldest son of Balaji Baji Rao, Peshwa of Pune (Poona) (the prime minister and de facto ruler/administrator) of the Maratha Empire and also was the heir to the title of Peshwa of Maratha Empire. He was killed during the period of the most intense fighting (Approx. between 01pm and 02:30pm) at Third Battle of Panipat, fighting on the front lines. It is generally accepted that the third battle of Panipat, which hung in balance till his death, moved decisively in favour of the Afghans and ended up in victory of Durrani Empire.
Although Vishwas Rao was first exposed to actual warfare at Sindkheda near Hyderabad, against Nizam in 1756, he was the nominal Commander of Maratha Forces and the Peshwa's representative during Third Battle of Panipat under guidance of his uncle Sadashivrao Bhau.
At the time of the battle, the Maratha Empire was in control of about 2/3rd of present India and some parts of Pakistan.