Yeah... that is bad but the post was getting too long as it were.

To give you guys an idea, this a video of someone fighting the boss...
YouTube - Persona 3 - Floor 135 ( "Boss - Sleeping Table" )

I would also like to give a shout out to most of the bosses in Shin Megami Tensei III Nocturne, yes, almost every boss in that game is "That One Boss" starting with the Matador Fiend and all the way to the final boss, only Dante offers a bit of a breather as far as boss battles go.

I would also like to nominate:



Miang/Opiomorph

Xenogears has a few "That One Boss" but most of them can be avoided if you know what't coming and prepare properly for it. Not for this fight. Its a Gear battle, your Gears don't level, rather you buy armor and engines to raise their HP, Defense, and attack power. So leveling is not going to help you much. Gears also rely on Fuel to do all the attacks and special abilites but its limited and although your Gears can recharge their fuel, its a pathetic amount without the aid of an accessory slot and there are still far better accessories (like ones that heal you)

Basically this is the second half of a two part sequential fight, the guy before her is not terribly powerful but he does have an attack that reduces your HP to one. Course you can use HP Frames to restore your health back but they cost huge amounts of fuel.

So you basically go into the Miang fight with at best, 50% of your health. She uses a special attack that llows her to hit your whole party with the accumulated damage your party has done to her which means you could easily lose if you are not paying attention to the dialogue on the scree, so you start having one character attack and wait for her to use the special attack (cause it resets after she uses it) to minimize damage but once she's lost half her health, she can start using the attack and do high damage without taking damage from you, worse, it gets stronger every round she's left alive... Throw in the fact the plot elements that happen right after are just a serious kick in the balls and you've got one of the most painful moments in gaming...