Ultimate Magic: Meteor is a fantastic board wipe, and the fact it can take out problem lands or artifacts as well as creatures makes it a very high pick for me
This splits the ripple vote a bit since demons dont synergize with the rats at all, but Shadowborn Apostle builds will want this card and thats good enough for some extra demand if people dont have the deck built yet
With the name You Are Already Dead, this will likely be the default named card for Tainted Pact combos in cEDH

Battle your way through the plane of Ikoria with monster-themed mechanics that grow your creatures build your bond and crush your opponents Symbiotic Swarm Commander (1) Planeswalker (1) Creatures (34) Cartographer's Hawk Sakura-Tribe Elder Satyr Wayfinder Aerial Responder Nikara, Lair Scavenger Nyx Weaver Skullwinder Solemn Recruit Splinterfright Vampire Nighthawk Angel of Finality Daring Fiendbonder Odric, Lunarch Marshal Slippery Bogbonder Tayam, Luminous Enigma Vitality Hunter Yannik, Scavenging Sentinel Acidic Slime Avenging Huntbonder Cairn Wanderer Cataclysmic Gearhulk Kalemne's Captain Karametra, God of Harvests Majestic Myriarch Reveillark Archon of Valor's Reach Soul of Innistrad Soulflayer Sunblast Angel Hornet Queen Akroma, Angel of Wrath Void Beckoner Zetalpa, Primal Dawn Titanoth Rex Instants (6) Abzan Charm Blood Curdle Deathsprout Despark Grisly Salvage Obscuring Haze Sorceries (7) Cultivate Harmonize Unbreakable Bond Unburial Rites Ever After Selective Adaptation Duneblast Enchantments (6) Together Forever Abzan Ascendancy Martial Impetus Parasitic Impetus Predatory Impetus Deadbridge Chant Artifacts (7) Sol Ring Arcane Signet Netherborn Altar Swiftfoot Boots Bonder's Ornament Commander's Sphere Mimic Vat Lands (38) Blighted Woodland Blossoming Sands Canopy Vista Caves of Koilos Command Tower Evolving Wilds Exotic Orchard Gavony Township Golgari Rot Farm Grim Backwoods Jungle Hollow Krosan Verge Memorial to Folly Myriad Landscape Nesting Grounds Orzhov Basilica Sandsteppe Citadel Scoured Barrens Selesnya Sanctuary Sungrass Prairie Forest x4 Plains x7 Swamp x7 Commander, Theme, and Strategy Kathril uses a feature introduced in Ikoria : placing keyword counters on creatures

Add in one more accelerant, like Birds of Paradise, Llanowar Elves, orheaven forbidSol Ring, and your hasted beater swells
It really shines in fairer matchups where forcing an opponent to either pay two mana for a Fatal Push/Lightning Bolt/Path to Exile or two-for-one themselves is a huge edge