UBR's best cards are big and expensive like Atraxa, Grand Unifier, Valgavoth, Terror Eater, and Indomitable Creativity, making Disdainful Stroke (4+ mana value) a premium counter. Mystical Dispute is cheap and can stop their Make Disappear, Fable of the Mirror-Breaker, or Negate while also hitting any blue permanents they commit. Lightning Axe is a liability since discarding into their Fable of the Mirror-Breaker or against a grindy matchup costs too much card advantage; Into the Flood Maw doesn't answer their enchantment-based threats like Fable or Unholy Annex-style engines (note: UBR here lacks that specific card, but similarly their Indomitable Creativity targets aren't bounced away for long). Prioritize countering their creature-lands-and-reanimation plan over racing.