Here’s my list. Some cards might be run maindeck, but they’re so good that I’ve included them (cards not in any particular order. Remember these are just the top 5 cards for each category based on popularity across different decks):

Colorless- Relic of Progenitus, Damping Sphere, Pithing Needle, Grafdigger’s Cage, Engineered Explosives

White- Rest In Peace, Stony Silence, Settle the Wreckage, Path to Exile, Leyline of Sanctity

Blue- Dispel, Negate, Echoing Truth, Thing in the Ice, Spell Pierce

Black- Surgical Extraction, Dismember, Collective Brutality, Damnation, Leyline of the Void

Red- Lightning Bolt, Anger of the Gods/Sweltering Suns, Abrade, Ancient Grudge, Grim Lavamancer

Green- Nature’s Claim, Scavenging Ooze, Reclamation Sage, Thrun, the Last Troll, Obstinate Baloth

Multicolored- Gaddock Teeg, Wear // Tear, Fulminator Mage, Maelstrom Pulse, Kitchen Finks

Edit: Replaced Gut Shot with Abrade. Edit 2: Replaced Eternal Witness with Obstinate Baloth, replaced Kambal with Kitchen Kinks, and replaced Naturalize with Thrun. Edit 3: Replaced Destructive Revelry with Fulminator Mage.

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I haven’t played against this list yet but have heard of it. I think it’s very rare for UW to just play 2 colors. What’s the tertiary color you are splashing? You could play alpine moon if you are splashing red. Or if you play black (like me) you could throw in an unmoored ego or two to hate out their key pieces like coffers, golos or Karn.

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The most underrated archetype in Modern rn imo More on reddit.com

Grave Hate and Artifact hate are must haves against an unknown field because you can pretty much always expect to find them. For griefblade you have access to all the great black and white sideboard cards. [[Sanctifier En-vec]] and [[Kataki, war's wage]] are pretty standard and hit those two areas. [[Damn]] is good vs any creature deck and [[Vindicate]] is a catch-all answer. For vindicate it's a little trickier because your curve is a lot lower and you don't want to diverge from your main gameplan too much but the same principles apply. Stuff like [[Nihil Spellbomb]], [[Force of Vigor]] and [[Assassin's Trophy]], hit those same fields. More on reddit.com