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.
Panzer III
Around the time of the beginning of Operation Barbarossa in the summer of 1941, the Panzer III was, numerically, the most important German tank on the frontline. At this time period, the majority of the available tanks (including re-armed Ausf. Es and Fs, plus new Ausf. G and H models) for the invading German military had the KwK 38 L/42 50mm cannon, which also equipped the majority of Panzer IIIs fighting in North Africa. Initially, the Panzer IIIs were significantly outclassed by the more-advanced Soviet T-34 medium and KV series of heavy tanks, the former of which was gradually encountered in greater numbers by the German forces as the invasion progressed. However, the most numerous Soviet tanks the Germans encountered at the start of the invasion were older T-26 infantry and BT class of cruiser tanks. This fact, together with superior German tactical and strategic skills in armoured clashes, sufficient quality crew training, and the generally-good ergonomics of the Panzer III, all contributed to a favourable kill-loss ratio of approximately 6 to 1 for German tanks of all types in 1941.