Stormcatch Mentor
The efficiency here will just put a really fast clock on your opponent, and I think thats enough for it to get into the lower range of bomb territory
The abilities in question are putting a +1/+1 counter on a creature and giving them First Strike until the end of the turn, creating a 2/2 token with Vigilance, and the ability to exile a tapped creature and gain two life
They copy themselves for each spell cast before it, so it's possible to cast enough spells to burn all your opponents with Grapeshot, or mill them all with Brain Freeze if you're able to cast a ton of spells in one turn (made easier with the Hullbreaker Horror combo)

Ruthless Regiment Deck List Commander (1) 1 Jirina Kudro Planeswalkers (1) 1 Nahiri, the Harbinger Creatures (32) 1 Kelsien, the Plague 1 Trynn, Champion of Freedom 1 Silvar, Devourer of the Free 1 Verge Rangers 1 Species Specialist 1 Titan Hunter 1 Fireflux Squad 1 Frontier Warmonger 1 Generals Enforcer 1 Bounty Agent 1 Dearly Departed 1 Frontline Medic 1 Knight of the White Orchid 1 Magus of the Disk 1 Odric, Master Tactician 1 Riders of Gavony 1 Thalias Lieutenant 1 Thraben Doomsayer 1 Disciple of Bolas 1 Xathrid Necromancer 1 Alesha, Who Smiles at Death 1 Captivating Crew 1 Fumiko the Lowblood 1 Magus of the Wheel 1 Titan of Eternal Fire 1 Adriana, Captain of the Guard 1 Banisher Priest 1 Cavalry Pegasus 1 Devout Chaplain 1 Zulaport Cutthroat 1 Humble Defector 1 Garna, the Bloodflame Spells (11) 1 Call the Coppercoats 1 Flawless Maneuver 1 Dire Tactics 1 Citywide Bust 1 Cleansing Nova 1 Increasing Devotion 1 Painful Truths 1 Ambitions Cost 1 Unexpectedly Absent 1 Crackling Doom 1 Terminate Artifacts (10) 1 Sanctuary Blade 1 Bonders Ornament 1 Arcane Signet 1 Boros Signet 1 Commanders Sphere 1 Heirloom Blade 1 Orzhov Signet 1 Rakdos Signet 1 Skullclamp 1 Sol Ring Enchantments (9) 1 Molten Echoes 1 Sanctuary Lockdown 1 Martial Impetus 1 Parasitic Impetus 1 Shiny Impetus 1 Bastion of Remembrance 1 Outpost Siege 1 Shared Animosity 1 Vigilante Justice Lands (36) 1 Battlefield Forge 1 Exotic Orchard 1 Shadowblood Ridge 1 Smoldering Marsh 1 Spinerock Knoll 1 Windbrisk Heights 1 Bojuka Bog 1 Boros Garrison 1 Command Tower 1 Myriad Landscape 1 Nomad Outpost 1 Orzhov Basilica 1 Path of Ancestry 1 Rakdos Carnarium 1 Temple of the False God 1 Unclaimed Territory 1 Bloodfell Caves 1 Evolving Wilds 1 Scoured Barrens 1 Wind-Scarred Crag 4 Mountain 8 Plains 4 Swamp Gavi, Nest Warden Gavi, Nest Warden ties into the returning mechanic of Ikoria : cycling

The follow-up set schedule matters because new synergies and counters can change what sells and plays