http://www.wowwiki.com/Corpse_Explosion

The ghoul is lost upon detonation but the amount of damage is significantly more than what is listed in the tooltip. This spell ignores resistance and resilience, the effect is similar (or possibly equivalent) to the self-destruction Explode ability a player gains when risen by a Death Knight using Raise Dead (pre-3.0.8), Raise Ally (post-3.0.7) or becoming a Risen Ghoul himself.