The Entire Crusades, especially the Third under King Richard of England. He achieved none of his goals, and ended with a political settlement that practically returned the Socio-Political-Economic situation in the Holy Lands to the original conditions before the original Crusades.

On another side, the Siege of Jerusalem by Saladin in 1187. The Jerusalem defenders attritted Saladin's forces to a dangerous level, for a city with negligble strategic advantage and was little more then a pile of rock after the Siege. The terms of Jerusalem's surrender was the same as the one Saladin first offered (perhaps he should've offered better terms the first time)...

So, Saladin lost a crap load of men for a city in the middle of now where and Balian of Ibelin bled the city dry for the exact same terms offered on Day One of the Siege...

Here is another one for you, Hitler's struggle for Stalingrad. Classic military cluster-fuque when he had a large force prepared to assault Moscow. And if the Moscow assaulters had the Stalingrad Army, perhaps Moscow could've been taken and the capital of a centrally controllled government would've been cut out. Like a spider web, cut out the center and the spider-web will not last much longer...