What is the largest tank?
Heavy tank
The Char 2C was one of the largest tanks ever produced. At the start of World War II, France and the Soviet Union were the only countries to have inventories of heavy tanks, such as the Char B1, T-35, and KV-1. The Matilda II was designed under the British infantry tank concept which is similar to the heavy tank having thick armor and weighing more than their other tanks. It’s usually separate because they have less firepower with their cruiser tanks (comparable to mediums) at the time having the same main armament but more machine guns. Later war examples were the German Tiger I and II, as well as the Soviet IS series. Note that "heavy" versus "medium" is more a question of tactical roles than weight; the Panther, for example, was a "medium" tank that outweighed most Allied "heavy" tanks.
Object 279
One of the reasons that this tank project was abandoned, as with other heavy tank projects, was that the Soviet military stopped operating with heavy fighting vehicles of that type, tanks and similar, as of 1960. Since then, the heaviest ones are kept at about 50 metric tons of weight, that is without counting in any extra equipment such as additional reactive armor, mine clearing devices (mine ploughs, mine rollers) etc. On July 22, 1960, at the demonstration of new technology on the range of Kapustin Yar, Nikita Khrushchev strictly forbade any tanks with a weight of more than 37 metric tons to be adopted by the military, having thus written off the entire program of heavy tanks that had proven to be so successful.