The most impossibly difficult enemy you've ever faced in any game..

[PullusPardus]

O_o your list is not really difficult.
there is a tactic with ruby weapon that will make the boss fight pretty short (of course you have to grind alot)
but other than that... i don't think that list is one of the difficult bosses in games. have you played FFX (international) FFXII and FFXI ?



Penance Final Fantasy X, that boss is really time consuming, (you can kill him with one hit )

but even that boss is far from being the toughest boss in games.