Disintegration is pretty much the ultimate way of killing someone. Oddly enough though, it's only a level 6 spell in Dungeons & Dragons, out of a list of nine spell levels. Which implies that roughly half the magic in existence is more powerful. (Actually somewhat less than that, since there are more spells per level at lower levels, but close enough.)

Having your component atoms ripped apart and scattered far and wide enough that there's no detectable trace of you left behind has to be pretty traumatic. Your Raise Dead spell is going to have a tough time of it. Particularly in settings where there is no Raise Dead spell.

Transcript

Darth Vader: Clones! Stop the intruders!
[SFX]: Pow!
Han: Run! C'mon, kid!
[SFX]: Pow!
Luke: He killed Obi-Wan!
Leia: The clones will kill you too if you don't move your butt!
Luke: So... is that it? Do we lose the game?
GM: No, we play on.
Luke: But... does he respawn?
[SFX]: Pow!
R2-D2: Heh. Obi-Spawn. No, I think Mr Rage-Quitter has quit for good here.
Obi-Wan's Pile of Robes: Neither rage, nor quit. I have merely transcended.
Luke: You freaking disintegrated so hard your robes didn't even have time to combust!
GM: In a hard science setting like this, a character who dies is dead for good.
Obi-Wan's Pile of Robes: Tell that to Anakin...