Dead vs DESTROYED

[garhkal]

AT what point in how much damage someone takes, does a person become totally destroyed (IE no raising possible, resurrection may be), vs just dead?

IE would someone who say had 13 hp left (its a brutal fight with a giant), who then get's critical hitted by the giant for 35hp of damage, just be dead, or would the blow have splatted him to where there would just be guts, gore and blood splatter all over?
What of the 20hp 6th level mage, who just got breathed on by a black dragon for 55hp?? Would any of him be left, to be hit by a raise dead??

In other words, At what point, do YOU SEE it, that the body's totally ruined, so Raise won't work, but resurrection will?
Is there a point, where even resurrection won't??

Is there (IYC) a minimum amount of the body, that must be present for a resurrection, or can someone just pull a hair out of a person, then use THAT to resurrect them later on??