Nicknamed the "Behemoth" by Soviet land forces, this tank was created with the intent to push on to Berlin. Single handedly, the amazing firepower wielded by the Kv-6 would have been ear shattering, but the fact that only 120mm of frontal armour were present meant it was in no way on par with the maus or e100 prototypes.
KV-6
The three turreted design was really a playoff on the success of the t-28 prototype in testing. Although an abysmally unreliable tank on the battlefield, the ability to use two cannons on separate turrets proved effective, unless the tank broke down before it got to the battlefield.
The KV-6 was actually rumored by German forces to have been fully completed. There are various accounts of engagements between German devisions and Behemoth tanks. One eye witness report claimed that a "KV-6 attempte to climb up a hill slope, at which point the central pressure caused it to crack and disabled it".
Another eyewitness report claims "regardless of the size of these soviet secret projects, our anti-armour artillery was capable of penetrating them quite easily". Although these reports were indeed credible, the Soviet Union did a wonderful job of hiding away whatever evidence of the KV-6 existed.
Only after the cold war did the blueprints and some other documents resurface, giving unique insight into this "land battleship" -- although not as magnificent as the monster or ratte.
In reality, the KV-6 would have to be matched in capability to the German "lowe super-heavy tank" . They shared relatively the same mobility, the same armour (although lowe clearly had more sloping) , and relatively the same guns (although Kv-6 didn't exactly have long, rifled guns like the lowe).
Kv VI
Perhaps the greatest thing that separates the KV-6 from the German and British super-heavy tanks is the fact that they did see combat (although not confirmed reliably). We can't imagine what a scary experience it would be to come across something like this, but the fear of engaging these was documented very clearly , as one man claimed "when we saw it (behemoth tank) in the distance, we began running [in the opposite direction] (sic)".
Magnificent and frightening, such is the reality of "secret projects".