Poll for you.

[Suicide Junkie]

I had a 200-ship fleet once.
150 dreadnoughts and battleships, assorted sweepers, and lots of troop transports.
All accompanied by a battlemoon loaded up with BioCrystal Armor.

We assaulted a Huge Norak Breathable world without and space force to speak of.

The evil planet was filled to the brim with horrible Massive Mount Talisman Death-Cannons.
It was such a horrific slaughter.
The survivors of the conflict numbered less than 25:
The sweepers that ran away, and the battlemoon with multi-thousand damage point scars on its armor.
All of the warships were dead. All of the transports that rushed the planet, including 50,000kt of infantry troops, all dead.

It wasn't a total loss, though.
20 turns later, a few thousand infantry units of the original 40,000 or so that reached the surface managed to capture the planet of 20 Billion people (Yes, more than the max)