A.G.D.B.

The Armored Gravity Defying Blimp is a late-game blimp conception that first appears on round 75. It's outer layer has 9,000 HP, and pops into 4 Steel Bloons. It has the properties of a lead bloon, but no other specials. It also moves suprisingly fast, at the speed of a blue bloon (Making it the second fastest Blimp when only considering the regular 4 blimps). However, it is extremely vulnerable to abilities, acting basically as a regular bloon in situations like these, despite having the HP & priority of a blimp (Being right above the BFB but below the ZOMG & DDT). It can easily be 1-shotted (No children) by things even a MOAB wouldn't be as severely effected by, such as the MOAB Assasin & Ground Zero.

Strategy
A.G.D.B.s are tough as many of your main MOAB-Popping towers may have no effect on it due to the lead property, leading to many almost completed games lost to it. However, there are several tips that can be used to defeat it.

First off, as said earlier, it is extremely vulnerable to abilities, allowing Ground Zero monkey aces to make quick work of them. MOAB assassins also do well, however they can only pop 1 at a time, but buying and reselling can be a good strategy until the randomly generated rounds (As the A.G.D.B. is third on the priority list, with ZOMGs & D.D.T.s being higher up on the list).

Otherwise, it is best to rely on multiple Sun Gods/Robo Monkeys to take care of it.

Trivia

 * It has suprisingly high HP on the outer layer, even more than the ZOMG, with the only reason it has a lower RBE is that it does not pop into a large variety of blimps, but simply 4 steel bloons. This arguably makes it the toughest bloon in the game (Not counting the khjillion other fan-made blimps).