The Maus, 192 tons of death on tracks.
Virtually impregnable.
Did you know that they considered using a submarine engine in this because of the immense power needed to move that amount of armour.
And as for the gun .... 128mm derived from the Pak44 atg, capable of destroying any Enemy tank at ranges of 2.5 kilometres.
But yes a failure.
It could be said it was TOO MUCH TOO LATE as recourses could have been better used putting into production the entwicklung/standardpanzer range of tanks.
Peace.