Here is one that knocked me out of my socks:

For the last month, I have been slowly playing through an ACW campaign ('61 with Kentucky events).
And then in the summer of 1863 I got to see the most stunningly stupid move, I have ever seen the Athena make.
In an all-out attack on Nashville basically Athena committed every possible mistake:
A. underestimating the enemy: I had retreated two corps from Kentucky a month earlier (supply problems + I wanted to keep my forces concentrated)
B. no reconnaissance: Athena had no way of knowing what I had sitting in the city. As it was to learn I had 90.000 men (the majority of my forces in the West, in ten divisions organized in two corps and an HQ stack), army commander was a certain Longstreet (with his insane defense value), the troops were well entrenched (level six) and had almost four hundred guns.
C. no coordinated movement: his five corps arrived one after the other over a span of eight days.
D. amphibious assault on a fortified position: three of those Union corps were sent via river transport
E. ignored fort: Fort Donelson wasn't taken first his amphibious assault forces passed the fort and got pounded by its guns on their way to Nashville
The result were three battles. Here are the casualties (Union first, then mine):
1) 13.000 - 300
2) 20.000 - 800
3) 35.000 - 1.000
Here is a screen of the last one:
[ATTACH]14938[/ATTACH]
I expect the onslaught to continue next turn, since one Union corps has yet to enter combat.
A disclaimer: I use a slightly modded version of ACW (inspired by RoP, I wrote some events that give the loosing side a massive boost in NM and ressources once its NM falls below a certain level. It makes for longer campaigns and goes a long way toward underlining the Norther superiority in manpower and industrial capacities).
Have you seen worse? Please share!