Jund Sacrifice is a low-curve creature swarm, so Day of Black Sun sweeps their army of 1-2 mana creatures like Callous Inspector, Gene Pollinator, and Greedy Freebooter cleanly. Duress strips their sideboard Strategic Betrayal or removal before they can use it on our threats, and it's live against their noncreature spells like Requiting Hex and Obsessive Pursuit. Witherbloom Charm's third mode kills their cheap mana-value-2-or-less permanents like Gene Pollinator or Greedy Freebooter. Negate is weak here since they run few noncreature spells worth countering, and Rapid Rescue/Wistfulness are too passive against a fast sacrifice deck.