Achilles' Blimp

Achilles' Bloon is an extremely powerful blimp (but doesn't carry any other blimps). When it comes to regular damage, it has health equal to Graham's number (so it's obviously not possible to defeat  However, it has an extreme weakness (its Achilles' heel). For unknown reasons, road spikes do huge amounts of damage to it. It only takes 20 sets of road spikes to destroy it.