At resolution, Complete Disregard will instead leave the stack and be put into its owner's graveyard without doing anything, because all its targets have become illegal.
Spells and abilities check for legality of their targets twice; once when you put them on the stack, and again when they resolve. If some, but not all, of its targets become illegal between the first and second check, the spell or ability resolves normally but does not affect or obtain information about illegal targets when it resolves. If all targets become illegal, the spell or ability does not resolve at all and, in the case of spells represented by cards, simply are put into their owner's graveyard.
- Resolving Spells and Abilities
608.2b If the spell or ability specifies targets, it checks whether the targets are still legal. A target that’s no longer in the zone it was in when it was targeted is illegal. Other changes to the game state may cause a target to no longer be legal; for example, its characteristics may have changed or an effect may have changed the text of the spell. If the source of an ability has left the zone it was in, its last known information is used during this process. If all its targets, for every instance of the word “target,” are now illegal, the spell or ability doesn’t resolve. It’s removed from the stack and, if it’s a spell, put into its owner’s graveyard. Otherwise, the spell or ability will resolve normally. Illegal targets, if any, won’t be affected by parts of a resolving spell’s effect for which they’re illegal. Other parts of the effect for which those targets are not illegal may still affect them. If the spell or ability creates any continuous effects that affect game rules (see rule 613.10), those effects don’t apply to illegal targets. If part of the effect requires information about an illegal target, it fails to determine any such information. Any part of the effect that requires that information won’t happen.