To kill most Megadeth, The “Last Resort” (ラスト-リゾート) was required. It is a “Houriki” 法力 (Magic Particle) based satellite weapon that had a destruction radius of several kilometers.
In the case of the Hydra (ヒュドラ), “Last Resort” ‘s destruction radius was 3 kilometers (after 3,000 residents were evacuated).
Because Last Resort can reduce all life to nothing within its space during the blast, no one can enter the kill-zone.
The charge time requirement of the Satellite is roughly 2000 seconds per 1.5 kilometers, even so it has a terrible effect on the environment and ultimately makes the target area a blockaded zone (or No-Man’s Land) for several hundred years.