K-Wagen another attempt of Nazi’s to build a super heavy tank and increase the assets in the armor corps. The K-Wagen lacked the main turret instead it had four 77 mm fortress guns mounted on the sides and seven machine guns. The ultimate weapon was deployed in the year 1917 and was second most successful and biggest tank ever built. The K-Wagen was 13 meters long, having the crew carrying capacity of 27 and weighed 120 tons.
#6 O-I: Japan
The O-I was a Japanese effort at building a super heavy tank. It has been reported that one model was accomplished and sent to Manchuria during WWII, but it is highly unlikely that the rumor is true. The O-I project was probably ended like all other super heavy tanks. The O-I was equipped with three turrets. The main turret had a 105 mm cannon, one of the minor turrets had a 37 mm cannon and the other minor turret had three machine guns. The tank was 10 meters long, weighed 130 ton and having a crew carrying capacity of 11 members.
#5 FCM F1: France
The FCM F1 is the heaviest and biggest tank not comparable to the Nazi’s ultimate destruction machines but It was supposed to replace the Char 2C, which is one of the heaviest tanks to ever see combat. Unfortunately France was defeated before the FCM F1 project was completed, so none of these tanks were ever built. The design was to build an enormous tank capable to outdo its competitor Char 2C in the battlefield; it was 11 meters long, with a crew carrying capacity of 9 personals and weighed 139 tons. The FCM F1 was supposed to have a 90 mm cannon, a 47 mm cannon and six machine guns. It is worth noticing that this tank was more than 10 meters long, but still only a little bit more than 3 meters wide so that it could be transported by train.
#4 E-100 Tiger-Maus: Germany
A super heavy tank analogous to the Panzer VIII Maus was supposed to be produced in the same year since after the discrepancies located in the previous version. The E-100 Tiger-Maus was light in weight which made it a better tank than Panzer VIII Maus, more agile and maneuverable. This project was also started in the year 1942, but no models were ever completed. A single hull was built in 1944, but no turret was fitted before the war ended. The E-100 Tiger Maus was supposed to use the same turret as the Panzer VIII Maus. Being lighter in weight it was more practical on the battlefield than Panzer VIII Maus.