Vaarna_Aarne
Notorious Internet Vandal
Actually only two of those tanks show up, and neither of them are beaten by just shooting at them (they're more like puzzle map, the second one even closer to being a puzzle map since the tank doesn't move and takes up most of the map). The closest thing to a giant tank besides those two is the armored train that's another bossfight.
EDIT: The second one is actually split into two chapters, the first one being a map where you need to run away before the giant fucking tank runs you over (you can find things to buy time on the way) while you lead it to a trap (the tank itself cannot be harmed because it's a giant fucking tank), the second one has you disable it for good (and it's here that it's closer to a level, the tank itself takes part in the fight only through its destructible turrets).
EDIT: The second one is actually split into two chapters, the first one being a map where you need to run away before the giant fucking tank runs you over (you can find things to buy time on the way) while you lead it to a trap (the tank itself cannot be harmed because it's a giant fucking tank), the second one has you disable it for good (and it's here that it's closer to a level, the tank itself takes part in the fight only through its destructible turrets).