AI War 2: Even Better Zenith Miner Visualss
Miners are able to eat an entire planet (shown first in this video, at 5x sim speed but animation speed -- time is compressed, but the animation is not sped up), and that literally leaves nothing behind. The planet is disconnected from the galaxy map and disappears, and once you leave you may never come back.
They can also ravage planets, which is what my last video earlier in the gay was about. In those cases, there's no more metal harvesters, but a nasty mostly-empty organic structure is left behind in the center of the grav well where the planet once was.
Both of these paths are working well now visually, and also include the planet bursting into flames 30 seconds (gametime) before the final destruction. If you can destroy the miner before it finishes its work, you can save the planet!