Stiflenought wins by using Stifle to counter the Phyrexian Dreadnought's triggered ability, getting a free 12/12 trampler, then protecting it with countermagic — your priority is disrupting their hand and tempo before they assemble the combo. Duress and Cabal Therapy are your best cards here, stripping Stifle and countermagic before you develop your threats. Chill is a powerful enchantment that taxes their blue spells heavily, since their entire deck is Islands and nearly every card is blue, effectively turning off their counter-suite. Defense Grid makes their instant-speed interaction (Counterspell, Foil, Daze) far more expensive on your turn, letting your threats and discard spells resolve cleanly. Smother, Snuff Out, and two Funeral Charms come out since their only creature is Phyrexian Dreadnought — a 12/12 you can't profitably remove — and the removal is largely dead.