One man's anticlimactic is another man's epic fail.
I started a fortress on top of an old mine inhabited by a cyclops. The first thing I did is lay a floor over the only stairwell access, then prepared my troops.
I tunneled down to the cyclops inside the walls of the mine, having to pierce an aquifer to do so.
Having finally marshaled my troops I established a barracks inside the walls in order to keep my soldiers there, gave them supplies, food and water and beds, then walled them off so that, should they fail, the earth itself would be their tomb. A lone miner in a separate squad was stuck in with them, also assigned to the barracks. His pick was on the floor, ready to be used.
I then prepared for a mighty cave-in to hopefully injure the cyclops before I let loose my troops on them. Here's what happened:
As I was waiting for somebody to install the support which would instigate the collapse, I discovered accidentally that I had left one diagonal selected for digging which shouldn't have been. Naturally the dwarf ran into the mine deciding to pick up a gem from the floor, and was eaten by the cyclops. Then another dwarf ran in to get his remains... You see where this is going.
Finally I decide in a panic to cut the support and sacrifice a dwarf so that the cyclops can't escape up the mine shaft I'd used to precipitate the collapse. One lone heroic peasant charges down and dismantles the support, causing a 1 level cave-in. The cyclops is out of range of the dust collapse, strolls in and finishes off the unconscious and mortally wounded peasant.
Due to a miscalculation on my part, the cave-in also collapses one corner of the wall to the barracks and the resulting dust cloud knocks out those soldiers who weren't already laying down on the job. The cyclops then strolls in and eats my entire sleeping army.
The remaining dwarves (now only 10) go mad and stop working (save the one which patches the entrances to the mines), half of them throw tantrums and kill almost the entire other half. The remainder wander around in the direst of moods despite the epicness of their dining rooms, alternately tantruming and going berserk. Finally the last dwarf left alive, somehow recovering from his melancholy begins burying the few corpses remaining. For no readily apparent reason (he may have had hunting turned on), he picks a fight with a camel and is stomped to death.
Edit: I did decide to reclaim that fortress. Due to the unholy amount of batmen present, it sent me with 7 squads of dwarves. To this mix I added 25 war dogs at the expense of supplies, knowing I could always reclaim it again later after the mines were gutted.
We arrived and delved into the mines only to find the cyclops completely gone and most of the batmen gone as well. After wandering around for 3 full months looking for them, I gave up and deactivated most of the military, continuing to build the original fortress to accommodate all of the new dwarves.
I left two units on circular patrol routes to make sure I didn't miss anything and caught a few batmen in ambush.
Then the cyclops arrives... and two wrestlers and 6 dogs kill the thing at the expense of one dog and one wrestler.