"Victim" refers to the target affected by Walking Bomb set to explode.
As the default Walking Bomb damage is based solely on 50% of the victim's maximum health, this ability doubles it to deal 100% of the victim's health. This allows the spell to instantly defeat any enemy of equal or lesser rank and health, provided they are vulnerable to spirit damage. As friendly fire damage is capped at 75% of your companions' health, sacrificing a companion who may yet survive to corral the entirety of an enemy group together at the moment of detonation can be a valuable tradeoff.
The ability checks for the Disorient status at the moment of the victim's death before issuing the 200% damage bonus or not. Therefore, the effect can be applied either before or after the bomb is cast, even at the very moment of death with a powerful ability like Disorienting Shot, and the explosion will deal 100% of the victim's health in damage. Should the Disorient effect be shed, such as changing the cross-class combo setup to Stagger or Brittle, wearing off naturally, or detonated with a talent or spell that exploits Disorient, the explosion will revert to its normal damage.